Existence of an Endocrine Gland in the Media of the Renal Arterioles

The juxta glomerular apparatus is composed mainly of smooth muscle cells devoid of myofibrils called afibrillar cells (abbr: a. f. cells). 2 , 4 In the superficial cortical zone of the normal kidney of the rabbit, these cell-groups show a glandular cycle culminating in the formation of acidophil or basophil secretion granules intermingled with minute vacuoles (Bouin-Hollande or Zenker-formol fixation). They are in close contact with the lumen of the vas afferens or with capillaries. The endocrine features of these cells are as definite as those of the chromophil cells of the anterior pituitary. Three weeks of moderate constriction of the left renal artery of young rabbits (Drury technic 1 ) which causes the shrinkage of a few glomeruli, are followed by an increase in number and size of the granulated cells in the superficial juxta glomerular apparatuses. (R. 31-91; 31-92; 31-93.) After the same lapse of time a more pronounced constriction causes the hyalinization of the superficial glomeruli and the regression of many tubuli, but leaves the renal arterioles patent. (R. 31-96; 31-97; 31-97). In these kidneys the increase in number of the granulated, a. f. cells is remarkable. Not only do they exist at the vascular pole of the intact or hyalinized glomeruli but they invade the latter and become conspicuous in the wall of all the arterioles of the cortex; a considerable number of smooth muscle cells still spindle-shaped, change into granulated a. f. cells. The granules become basophil. (Masson's trichrome technic.)

Identical changes occur in the ischemic kidney of the dog, but are not so readily recognized because the a. f. cells do not contain secretion granules normally. From a renewed survey of the ischemic kidneys of the 12 dogs referred to in a previous communication 3 the behavior of the a. f. cells in acute or subacute experiments can be summarized as follows: hypertrophy, hyperplasia and vacuolation of the a. f. cells of the juxta glomerular apparatus; occasional protrusion of the a. f. cells in the glomerular tuft; hyperplasia of the a. f. cells of the vas afferens followed by glomerular regression; transformation of ordinary smooth muscle cells into a. f. cells: a process which is accompanied by mitotic activity.