Some Observations on Circulatory Changes in a Renal Glomerulus

Abstract

In a female Necturus, anesthetized with urethane, a glomerulus showing sluggish blood flow was observed; the capillary loops were dilated, although not uniformly. The picture was unchanged by pithing the brain. This glomerulus was peculiar in that both afferent and efferent vessels were clearly seen; the afferent vessel came direct from a large ovarian artery. There was no alternation of flow. The afferent vessel was now stroked gently with a fine glass rod; there was no response. More vigorous stroking resulted in a shifting of the kidney region in the field after about a 5 second latent period; this was followed in 5 seconds more by constriction of the afferent vessel to the point of cessation, complete or practically so, of cell movement in the glomerulus. The shifting of the kidney region preceding afferent vessel constriction was seen to be due to a contraction of the ovarian artery from which the afferent vessel sprang, resulting in a tugging on the kidney. It was then found that traction on the ovarian artery was an adequate stimulus to this vasoconstriction, which spread from the artery to the afferent vessel. After this experiment had been repeated a few times at intervals of 3 or 4 minutes the phenomenon would occur without external stimulation; previous to its first production the flow had been steady for the 20 minute period of observation.

Both between and during periods of afferent vessel constriction the efferent vessel was seen to be constantly constricted, being narrower than the narrowest loop in the capillary tuft. Cells passed through it rapidly and in single file. Actual observation of such a constricted efferent vessel strengthens an idea which has been held for some time, that the slow blood flow through dilated glomerular capillaries at a time when the general circulation is vigorous is due to efferent vessel spasm.