On histochemical studies of the various organs of spontaneously hypertensive rats.

Spontaneously hypertensive rats (OKAMOTO and AOKI) were sacrificed in the pre-hypertensive stage (40 to 60 days after birth), initial stage (5 to 7 months after birth) or advanced stage of hypertension (13 to 17 months after birth). Twenty-one kinds of enzyme activity were examined histochemical in the adrenals, thyroid, kidneys, heart, liver and pancreas, and noradrenalin reaction was also applied to the adrenal medulla. Each positive finding in spontaneously hypertensive rats was obtained by comparing it with the reaction of the same sex normotensive Wistar strain rats with almost the same survival duration. 1) Glucose-6-phosphate dehydrogenase and triphosphopyridine nucleotide diaphorase activity increased in the zona fasciculata and reticularis of the adrenal cortex of spontaneously hypertensive rats with dominant elevation of the former activity in the middle and outer part of the fascicular zone from the pre-hypertensive stage. More prominent increase was observed after the incidence of hypertension. 2) The noradrenalin-storing cell islets in the adrenal medulla of spontaneously hypertensive rats indicated a stronger reaction with about twice the mean dimensional ratio to the whole adrenal medulla in all stages than was found in normotensives. 3) Acid phosphatase activity in the follicular cells of the thyroid in spontaneously hypertensive rats was elevated from the pre-hypertensive stage. 4) Adenosine triphosphatase activity of the renal interlobular arteries of spontaneously hypertensive rats showed an increase in about half the cases in the pre-hypertensive stage and in all cases after the incidence of hypertension. 5) Glucose-6-phosphate dehydrogenase and triphophopyridine nucleotide diaphorase activity in the zona glomerulosa of the adrenal cortex of spontaneously hypertensive rats rose after the incidence of hypertension, though the latter activity showed only a slightly in-creasing tendency. 6) Increase of adenosine triphosphatase activity in the walls of renal interlobular arteries and vasa afferens of spontaneously hypertensive rats was detected in all cases after the incidence of hypertension. 7) Gradual elevation of monoamine oxidase activity in the heart muscle of spontaneously hypertensive rats occurred after the incidence of hypertension. 8) No constant difference was found in the results of other kinds of enzyme histochemical comparisons of adrenals, thyroid, kidneys or heart, or in the enzyme histochemistry of the liver or pancreas, either. 9) From the above-mentioned evidence, it may be assumed that there exists from the pre-hypertensive stage in spontaneously hypertensive rats, an increase of (1) glucocorticoids synthesis in the adrenal cortex ; (2) either synthesis of noradrenalin, or retention of it in the adrenal medulla ; (3) secretory activity of the thyroid and (4) the contracting tendency of the renal vessels of medium caliber. In addition, after the incidence of hypertension, elevation of (5) aldosterone synthesis in the zona glomerulosa of the adrenal cortex ; (6) the contraction of the renal vessels and (7) the catecholamine metabolism, primarily the oxidative deamination in the heart muscle is also indicated.