Cortical and Medullary Canine Renal Lymph Formation during_ Acetylcholine Induced Renal Vasodilation *

Abstract

It is widely held that both corlex and medulla of the mammalian kidney participate
in renal lymph formation ( 1). The influence of the renal cortex on renal lymph composition
is demonstrated by renal lymph to arterial plasma ratios less than unity for inulin
(2), creatinine (3) and p-aminohippurate (PAH) (4). The finding that cortical extraction
of inulin is reflected in the renal lymph concentration of that substance promoted the
hypothesis that renal lymph may be derived from both blood plasma and tubular reabsorbate
(2). More detailed information concerning the mechanisms of cortical renal
lymph formation requires further experimentation.
Lymph formation in the r.enal medulla is well supported by anatomical findings in
the human kidney (5, 6). Even so, it has not yet been possible to demonstrate changes
in canine renal lymph composition when medullary function is altered (3, 7). Thus,
additional data are needed to establish the importance of the medulla in renal lymph
formation.
The experiments of the present study are based on the finding that the capsular lymphatic
vessels of the canine kidney drain primarily the cortex, while the hilar l ymphatic
vessels are believed to drain both cortex and medulla (8). The avid cortical extraction
of PAH and the absence of protein from tubular reabsorbate make these two substances
of particular interest. Additional informa tion concerning both cortical and medullary
renal lymph can thus be gained by determining capsular and hilar renal lymph concentrations
of P AH and protein before and during changes in renal hemodynamics such
as those produced by acetylcholine (ACh).