Does alkalosis per se or does the associated lactacidemia determine the rate of PAH or Diodrast transport? How is net renal uptake of lactate related to Tmpah? Tmpah, renal extraction of I131-Diodrast (Ediod) and net renal lactate uptake were studied in anesthetized (pentobarbital) dogs. In clearance experiments, Tmpah is elevated (facilitated) by isohydric increases in blood [lactate]; alkalosis has no further effect on the facilitated (by lactate) Tmpah. In contrast to the effects of alkalosis on Tmpah, no rise in Ediod occurs during alkalosis. However, when Ediod is depressed by [PAH] sufficiently high to achieve Tmpah, a rise in blood lactate does enhance Ediod. Thus, lactate enhances Ediod when the transport mechanism common to it and PAH is saturated. Net renal uptake of endogenous lactate is decreased during alkalosis; no net renal production of lactate has been observed. Therefore, the increases in Tmpah and Ediod are not related to a rise in net renal uptake of lactate but are probably more related to the blood [lactate]. It is postulated that Tmpah and Ediod may be more dependent on the metabolic mixture presented to the kidney, and thus on extrarenal metabolism, than on intrarenal distribution of blood flow or rate of renal blood flow.
Intrarenal Distribution of Blood Flow in Dogs during Hemorrhagic Hypotension