# Thomas (Tom) B. Bolton – a major force in smooth muscle research

Alexander V. Zholos<fnref n="1" /> ID, Iain A. Greenwood<fnref n="2" />, Rick J. Lang<fnref n="3" />, Christopher D. Benham<fnref n="4" />,
Philip I. Aaronson<fnref n="5" /> ID, Christopher J. Garland<fnref n="6" /> ID, Arthur H. Weston<fnref n="7" /> ID, Sally A. Prestwich<fnref n="8" />,
Dmitri V. Gordienko<fnref n="9" />, Oleksandr V. Povstyan<fnref n="10" />, Hailin Zhang<fnref n="11" />, Lucie H. Clapp<fnref n="12" />, Vladimir Pucovsky<fnref n="13" />,
Marianne Tare<fnref n="14" /> ID, Claire J. Fenech<fnref n="15" />, Toshihiro Unno<fnref n="16" />, Katsuhiko Muraki<fnref n="17" />, Jian Shi<fnref n="10" />,
Alun D. Hughes<fnref n="12" /> ID, Thomas K. Halstead<fnref n="18" /> and David J. Beech<fnref n="10" /> ID

Handling Editor: Kim Barrett

The peer review history is available in the Supporting Information section of this article
(https://doi.org/10.1113/JP287062#support-information-section).

(Received 14 June 2024; accepted after revision 14 June 2024; first published online 26 June 2024)

Email: d.j.beech@leeds.ac.uk

<figure><img src="image_1.png" /></figure>

Tom was born on 14 November 1941 to Tom and Winnie (née Halstead) in Sunderland, England. His father was killed in July 1941 when his aeroplane was shot down over the North Sea. Winnie and Tom settled in Yeadon, West Yorkshire, and Tom was educated nearby, at Woodhouse Grove School. He obtained a First Class Honours Batchelor of Science degree in Physiology at the University of London in 1964 and a PhD in Pharmacology in 1967, which he passed after examination by the eminent pharmacologist Sir John Vane. He subsequently

completed a Bachelor of Veterinary Medicine and was admitted to the Royal College of Veterinary Surgeons as a practising veterinary surgeon. He remained active as a vet and was for many years the vet responsible for the animal facility at St George's Hospital Medical School (now St George's University of London), which was where he dedicated most of his working life to teaching, research and university leadership.

Tom first became interested in research and particularly smooth muscle research through his time at the Department of Pharmacology, Oxford University, where he was a Royal Society Locke Research Fellow at Brasenose College. He was greatly inspired by the

<figure><img src="image_2.png" /></figure>

<footnote n="1">¹Taras Shevchenko National University of Kyiv, Kyiv, Ukraine</footnote>

<footnote n="2">²St George's University of London, London, UK</footnote>

<footnote n="3">³Monash University, Melbourne, Victoria, Australia</footnote>

<footnote n="4">⁴University of Hertfordshire, Hatfield, UK</footnote>

<footnote n="5">⁵King's College London, London, UK</footnote>

<footnote n="6">⁶University of Oxford, Oxford, UK</footnote>

<footnote n="7">⁷University of Manchester, Manchester, UK</footnote>

<footnote n="8">⁸Horsham, UK</footnote>

<footnote n="9">⁹Inserm U1003, Université de Lille, Villeneuve d'Ascq, France</footnote>

<footnote n="10">¹⁰University of Leeds, Leeds, UK</footnote>

<footnote n="11">¹¹Hebei Medical University, Shijiazhuang, China</footnote>

<footnote n="12">¹²University College London, London, UK</footnote>

<footnote n="13">¹³European Medicines Agency, Amsterdam, The Netherlands</footnote>

<footnote n="14">¹⁴Monash University Melbourne, Melbourne, Victoria, Australia</footnote>

<footnote n="15">¹⁵CNRS UMR6265 – CSGA, Dijon, France</footnote>

<footnote n="16">¹⁶Gifu University, Gifu, Japan</footnote>

<footnote n="17">¹⁷Aichi-Gakuin University, Nagoya, Japan</footnote>

<footnote n="18">¹⁸University of York, York, UK</footnote>
late Edith Bülbring, who lived until 1990 and is widely regarded as the mother of smooth muscle physiology. In 1976, Tom became Senior Lecturer at St George's. Within 4 years he was professor, and 5 years later he became Head of the Department of Pharmacology and Clinical Pharmacology. He subsequently spent 4 years as the Dean of Research and Development at St George's. He served on Wellcome and British Heart Foundation grant panels, was chair of a Higher Education Funding Council Basic Medical and Dental Science Research Assessment Exercise panel and non-executive director at St Hellier's Healthcare Trust. He was a member of the British Pharmacological Society, Physiological Society, Biophysical Society, Save British Science, Biochemical Society, Universities Federation for Animal Welfare and Royal College of Veterinary Surgeons. In 1998 he was elected to Fellowship of the Academy of Medical Sciences and the Academia Europaea in recognition of his outstanding contributions.

Tom built a world-leading smooth muscle research group. 'The Smoothies' specialized in investigating ionic events and associated ion channels of smooth muscle cells. These cells quietly, subconsciously but critically determine movements of fluids and substances in tubes and containers throughout the body. Tom's group was in the vanguard of research that used new technologies (single-cell patch-clamp electrophysiology and laser confocal imaging), and he established many international collaborations as a consequence. He was a master of the single and double sucrose gap techniques and hand-built some of his laboratory's early patch-clamp equipment. In the autumn of 1981, he returned from a lecture tour with a small brown envelope. He had been to A. M. (Buzz) Brown's laboratory in Texas, where he had been given two 1 GΩ resistors, which were essential components of the patch-clamp head stage and difficult to obtain. The equipment Tom then built was used to make many published patch-clamp recordings from smooth muscle cells until commercial amplifiers became available. The laboratory was truly pioneering.

Tom was especially interested in ionic events evoked by acetylcholine acting on intestinal smooth muscle cells to regulate gut motility. He described membrane depolarizing effects (Bolton, 1971, 1972) and used microelectrodes and voltage clamp to characterize them further (Bolton, 1975). He applied newly emerging patch-clamp and cell-isolation techniques to prove that underlying the depolarization was a non-selective cationic transmembrane inward current (Benham et al., 1985). He showed the relationship with intracellular calcium concentration (Pacaud & Bolton, 1991), roles of G proteins (Komori & Bolton, 1990) and types of muscarinic receptor (Zholos & Bolton, 1997). He revealed the voltage dependence of the ionic mechanism and pointed

to involvement of non-selective cationic channels that are now known as transient receptor potential or TRP channels (Zholos et al., 2004). He showed that several principles were relevant to the actions of other transmitters, such as noradrenaline, on arterial smooth muscle cells (Bolton et al., 1984). He inspired the field with seminal review articles on the mechanisms of action of transmitters and other substances (Bolton, 1979) and excitation-contraction coupling (Bolton et al., 1999) in smooth muscles.

Tom and colleagues recognized that the depolarizing effect did not occur in isolation. His team identified spontaneous transient outward currents (Benham & Bolton, 1986), properties of calcium stores (Bolton & Lim, 1989) and calcium release events induced by inositol 1,4,5-trisphosphate (Komori & Bolton, 1991). He introduced new calcium-imaging techniques to observe the calcium events and their subcellular distribution in real time (Imaizumi et al., 1998) and crosstalk between different intracellular calcium-release channels (Gordienko & Bolton, 2002). Tom and his team combined confocal laser scanning microscopy with simultaneous patch-clamp recordings for direct visualization of subcellular calcium signalling acting at ion channels, developing a 'local calcium control' concept (Gordienko et al., 1999) that built on the original spontaneous transient outward current observations. Spatial organization of the calcium in the endoplasmic reticulum and mitochondria was revealed (Gordienko et al., 2001).

His group described depolarization-activated calcium currents (Aaronson et al., 1988) and the counterbalancing potassium channel mechanisms. As such, his group was one of the first to characterize calcium-activated potassium channel (Benham et al., 1986) and delayed rectifier potassium channel currents in smooth muscle cells (Beech & Bolton, 1989). Tom's group identified two types of ATP-sensitive potassium channels in smooth muscle, one of which was activated by nucleotide diphosphates (Beech et al., 1993; Zhang & Bolton, 1996), and a hyperpolarization-activated current mediated by potassium and sodium ions (Benham et al., 1987). His group was among the first to describe endothelium-dependent hyperpolarization regulating adjacent smooth muscle cells (Bolton & Clapp, 1986; Bolton et al., 1984) and to recognize interstitial cells in the vascular wall (Povstyan et al., 2003; Pucovsky et al., 2003). His interests extended to eosinophils, in which his team characterized proton currents (Gordienko et al., 1996). Tom was known to roll up his sleeves and fearlessly perform venepuncture on himself to donate blood for the experiments!

In 2005, there was celebration of Tom's scientific contributions with a Physiology Society meeting in Oxford, bringing together investigators from across
the world. In 2011, he was awarded an Honorary Doctorate from Kingston University in recognition of his outstanding contributions and development of teaching. At the ceremony he said, 'I would say there are no short-cuts. Understand everything you do 100 per cent at each and every stage, be prepared to work long hours, be almost zealot-like in your approach, learn how to fight off bureaucrats – only then will you have the drive and knowledge to succeed.' Those who knew Tom will recognize his character from this statement and remember him fondly. As a PhD student working in another institution was once told, 'practise your talk well because Tom Bolton is likely to be present'. He was a yardstick of quality. He valued thoroughness and, above all, critical straightforward thinking, and tolerated no nonsense.

Many of the people who trained with Tom went on to senior positions across the globe fuelled by his relentless work ethic. Investigators inspired by him and whom he supported in many ways were from countries including Australia, Bulgaria, China, France, Germany, Japan, Slovakia, Ukraine and the USA. He inspired the next generation of investigators, many of whom were very fortunate to have worked with him, and so the research goes on, but his energy and contributions will be missed.

Tom was a ferocious competitor on the squash court and five-a-side pitch, especially when his eyes had gone a bit – ouch! He was a keen weightlifter, lover of fast driving in high-end cars, which he serviced himself, and big fan of curries. A do-it-yourself enthusiast, he repaired, improved and extended his house in South Nutfield. He also had an old tractor, which he used to mow the grass in the field where his rather intimidating Dobermann pinscher dogs could exercise. With up to five of them in the house, it could be difficult to find a place to sit. Pat (née Moore, whom he married in 1961) exhibited the dogs at Crufts. Fairly recently, he hired, and learned to operate, a digger, just to bury one of his dogs on his property. He was indefatigable in battling against any authority, including water companies, banks, hospital trusts and social services.

Pat died in 2017 and his second son, Nicholas, in 2008. Tom is survived by his sons Grant and Kirk and five grandchildren.

Tom passed away after a short illness on 27 May 2024.

## References

Aaronson, P. I., Bolton, T. B., Lang, R. J., & MacKenzie, I. (1988). Calcium currents in single isolated smooth muscle cells from the rabbit ear artery in normal-calcium and high-barium solutions. *The Journal of Physiology, 405*(1), 57-75.

Beech, D. J., & Bolton, T. B. (1989). Two components of potassium current activated by depolarization of single smooth muscle cells from the rabbit portal vein. *The Journal of Physiology, 418*(1), 293-309.

Beech, D. J., Zhang, H., Nakao, K., & Bolton, T. B. (1993). K channel activation by nucleotide diphosphates and its inhibition by glibenclamide in vascular smooth muscle cells. *British Journal of Pharmacology, 110*(2), 573-582.

Benham, C. D., & Bolton, T. B. (1986). Spontaneous transient outward currents in single visceral and vascular smooth muscle cells of the rabbit. *The Journal of Physiology, 381*(1), 385-406.

Benham, C. D., Bolton, T. B., Denbigh, J. S., & Lang, R. J. (1987). Inward rectification in freshly isolated single smooth muscle cells of the rabbit jejunum. *The Journal of Physiology, 383*(1), 461-476.

Benham, C. D., Bolton, T. B., & Lang, R. J. (1985). Acetylcholine activates an inward current in single mammalian smooth muscle cells. *Nature, 316*(6026), 345-347.

Benham, C. D., Bolton, T. B., Lang, R. J., & Takewaki, T. (1986). Calcium-activated potassium channels in single smooth muscle cells of rabbit jejunum and guinea-pig mesenteric artery. *The Journal of Physiology, 371*(1), 45-67.

Bolton, T. B. (1971). On the nature of the oscillations of the membrane potential (slow waves) produced by acetylcholine or carbachol in intestinal smooth muscle. *The Journal of Physiology, 216*(2), 403-418.

Bolton, T. B. (1972). The depolarizing action of acetylcholine or carbachol in intestinal smooth muscle. *The Journal of Physiology, 220*(3), 647-671.

Bolton, T. B. (1975). Effects of stimulating the acetylcholine receptor on the current-voltage relationships of the smooth muscle membrane studied by voltage clamp of potential recorded by micro-electrode. *The Journal of Physiology, 250*(1), 175-202.

Bolton, T. B. (1979). Mechanisms of action of transmitters and other substances on smooth muscle. *Physiological Reviews, 59*(3), 606-718.

Bolton, T. B., & Clapp, L. H. (1986). Endothelial-dependent relaxant actions of carbachol and substance P in arterial smooth muscle. *British Journal of Pharmacology, 87*(4), 713-723.

Bolton, T. B., Lang, R. J., & Takewaki, T. (1984). Mechanisms of action of noradrenaline and carbachol on smooth muscle of guinea-pig anterior mesenteric artery. *The Journal of Physiology, 351*(1), 549-572.

Bolton, T. B., & Lim, S. P. (1989). Properties of calcium stores and transient outward currents in single smooth muscle cells of rabbit intestine. *The Journal of Physiology, 409*(1), 385-401.

Bolton, T. B., Prestwich, S. A., Zholos, A. V., & Gordienko, D. V. (1999). Excitation-contraction coupling in gastrointestinal and other smooth muscles. *Annual Review of Physiology, 61*, 85-115.

Gordienko, D. V., & Bolton, T. B. (2002). Crosstalk between ryanodine receptors and IP(3) receptors as a factor shaping spontaneous $Ca^{2+}$-release events in rabbit portal vein myocytes. *The Journal of Physiology, 542*(Pt 3), 743-762.
Gordienko, D. V., Greenwood, I. A., & Bolton, T. B. (2001). Direct visualization of sarcoplasmic reticulum regions discharging $Ca^{2+}$ sparks in vascular myocytes. *Cell Calcium*, **29**(1), 13–28.

Gordienko, D. V., Tare, M., Parveen, S., Fenech, C. J., Robinson, C., & Bolton, T. B. (1996). Voltage-activated proton current in eosinophils from human blood. *The Journal of Physiology*, **496**(Pt 2), 299–316.

Gordienko, D. V., Zholos, A. V., & Bolton, T. B. (1999). Membrane ion channels as physiological targets for local $Ca^{2+}$ signalling. *Journal of Microscopy*, **196**(Pt 3), 305–316.

Imaizumi, Y., Torii, Y., Ohi, Y., Nagano, N., Atsuki, K., Yamamura, H., Muraki, K., Watanabe, M., & Bolton, T. B. (1998). $Ca^{2+}$ images and $K^+$ current during depolarization in smooth muscle cells of the guinea-pig vas deferens and urinary bladder. *The Journal of Physiology*, **510**(Pt 3), 705–719.

Komori, S., & Bolton, T. B. (1990). Role of G-proteins in muscarinic receptor inward and outward currents in rabbit jejunal smooth muscle. *The Journal of Physiology*, **427**(1), 395–419.

Komori, S., & Bolton, T. B. (1991). Calcium release induced by inositol 1,4,5-trisphosphate in single rabbit intestinal smooth muscle cells. *The Journal of Physiology*, **433**(1), 495–517.

Pacaud, P., & Bolton, T. B. (1991). Relation between muscarinic receptor cationic current and internal calcium in guinea-pig jejunal smooth muscle cells. *The Journal of Physiology*, **441**(1), 477–499.

Povstyan, O. V., Gordienko, D. V., Harhun, M. I., & Bolton, T. B. (2003). Identification of interstitial cells of Cajal in the rabbit portal vein. *Cell Calcium*, **33**(4), 223–239.

Pucovsky, V., Moss, R. F., & Bolton, T. B. (2003). Non-contractile cells with thin processes resembling interstitial cells of Cajal found in the wall of guinea-pig mesenteric arteries. *The Journal of Physiology*, **552**(Pt 1), 119–133.

Zhang, H. L., & Bolton, T. B. (1996). Two types of ATP-sensitive potassium channels in rat portal vein smooth muscle cells. *British Journal of Pharmacology*, **118**(1), 105–114.

Zholos, A. V., & Bolton, T. B. (1997). Muscarinic receptor subtypes controlling the cationic current in guinea-pig ileal smooth muscle. *British Journal of Pharmacology*, **122**(5), 885–893.

Zholos, A. V., Zholos, A. A., & Bolton, T. B. (2004). G-protein-gated TRP-like cationic channel activated by muscarinic receptors: Effect of potential on single-channel gating. *Journal of General Physiology*, **123**(5), 581–598.

## Additional information

### Competing interests

None.

### Author contributions

All authors have approved the final version of the manuscript and agree to be accountable for all aspects of the work. All persons designated as authors qualify for authorship, and all those who qualify for authorship are listed.

### Funding

None.

### Keywords

calcium current, calcium dynamics, electrophysiology, gastrointestinal smooth muscle, ion channel, patch clamp, smooth muscle, vascular smooth muscle

## Supporting information

Additional supporting information can be found online in the Supporting Information section at the end of the HTML view of the article. Supporting information files available:

### Peer Review History