Sydney Ringer; physiological saline, calcium and the contraction of the heart

Sydney Ringer’s four papers published in The Journal of Physiology in the early 1880s (1882a,b, 1883a,b) are rightly acknowledged as the starting point for the development of the modern understanding of the role of calcium in the contraction of the heart. In them, Ringer established the relative importance, both qualitative and quantitative, of sodium, potassium and calcium ions, as well the longerterm necessity to prevent or reverse the acidification associated with contraction. What emerges is the precise composition of a ‘saline’ able to maintain the normal heart beat form and frequency for several hours. This ‘saline’ is ‘Ringer’s solution’. It is the precursor of all subsequent ‘physiological salines’ and related media that have enabled normal cell function to be sustained and studied in vitro. It provided the basis for salines infused into animals and humans, both experimentally and clinically, the latter a critical prerequisite for much modern medicine and surgery, both specifically in cardioplegia, but far more generally too. As we now understand more clearly, the heart provides a bioassay responsive to both electrophysiological (spontaneous beating) and contractile (calcium-entry dependent) consequences of the composition of the bathing solution. By focussing on the heart, Ringer’s studies enjoyed an exquisite sensitivity to subtle variations of the ionic composition of bathing solutions. The fortuitous choice of the heart ensured that his conclusions apply to all cells and tissues. Ringer’s definitive final paper in the ‘calcium’ series (1883a) has been cited – mostly correctly for pagination, etc. – over 600 times in the last 20 years. However, citation analysis reveals (Simkin & Roychowdhury, 2003) that we can be confident that far fewer than these 600 ‘citers’ will actually have read the papers. As we pass the 120th anniversary of the publication of Ringer’s papers, and approach the centenary of his death in 2010, what can be made of them, especially with the rose-tint of hindsight removed? First, some pointers on features unusual for the modern reader. There are superficial distractions encountered when reading papers from the 1880s. In 2004, one is surprised to find that the word ‘frog’ is not to be found in the main calcium papers at all. However, the animal used is clear, for example, in Ringer’s first paper in volume 3 (1882c, on the influence of season and temperature on drug actions). Rana temporaria is only cited explicitly in Ringer & Sainsbury, (1883). In this lack of detail, and many other methodological points, the reader is clearly assumed to be fluent with the scientific literature, the techniques, the fashionable questions and leading scientific personalities of the day. There are few recognizable references but a rather more frequent name dropping. It helps to recall that Ringer had already demonstrated the ‘actions of lime and potash salts on the ventricle’ to members of the Physiological Society at the University College London meeting in December 1882 (he became a member in 1884). His papers, and many of the others in these early volumes, indeed read more like house journals circulating amongst colleagues than the stylised, detached tone that we encounter in the modern literature. The text of papers of the period is not broken into Methods, Results, etc., but – in Ringer’s papers in particular – read more like an experimental diary and discourse upon experiments done. Some authors did provide overall conclusions, to help their audience, but not Ringer. There are few graphical representations (other than anatomical) within contemporaneous papers, but engravings of kymograph smoked-drum traces are presented as foldout ‘plates’ at the end of the volume. (Those familiar with such methods, still standard for undergraduates into the 1970s, will be impressed by the evident skill involved. The variable use of Roman and Arabic numerals between the plates and the main text increases the challenge of interpretation). Results tables are also rare and there is nothing statistical, of course, except in one paper where Ringer (1882c) does report ‘average responses’. (Pearson, one groundbreaker of statistics as applied to biological and experimental questions, did not start this work until the 1890s; others such as Spearman and Fisher came later still. Incidentally, all three, like Ringer, worked at University College London). Ringer also comments elsewhere that a few repeated observations were insufficient to permit him to draw firm conclusions; n numbers were evidently a matter of concern even in 1882–3. Despite these superficial challenges, one soon gains an impression of a confident, meticulous, observant and insightful experimentalist at work. The (physio)logic of Ringer’s approach chimes completely with that of the 21st century. As you read, you find yourself barely ahead of Ringer, despite the 120-year scientific advantage, our easy access to fine chemicals and extraordinary technological advantages. For example, at one stage (1882b, p. 383) he focuses quickly on potassium itself, rather than the attendant anions in the salts he was testing, as one key ingredient for a saline to maintain, or restore, normal function. Thus, he reports on potassium chloride, -phosphate, -sulphate, -citrate, -carbonate and -bicarbonate, -chlorate, -nitrate and -acetate in a few pithy sentences. In the same paper, the positive actions of serum albumin were carefully observed and understood; he had dialysed lambs’ serum for 4 days, rendering it ineffective once shorn of its attendant ions – predominantly potassium, as he knew. Ponder doing this study yourself without a shelf of catalogues or telephone ordering; nor with a pH-meter, digital balance or modern pipette in sight. (Ringer (1883a) refers to chemicals prepared by a Mr Lawes and Mr Page or, commercially, from the firm of Hopkins & Williams, which provided the distilled water which eventually proved so crucial). The amphibian heart is well suited to Ringer’s technique because it has no coronary vascular supply; the extracellular space of the myocytes is freely contiguous with the contents of the ventricular lumen. The spongiform myocardial matrix within a gross trabecular structure thus allows for rapid extracellular exchange, even with a mechanically robust structure the size of a frog’s ventricle. Indeed, even 80 years later, the superfused half-ventricle