Proximal luminal diameters and cell volume in rats anesthetized with inactin and amytal

Tubulo-glomerular feedback response: enhancement in adult spontaneously hypertensive rats and effects of anaesthetics

Open-loop tubulo-glomerular feedback (TGF) responses were measured in halothane anaesthetized spontaneously hypertensive rats (SHR), in normotensive Wistar Kyoto (WKY) and Sprague-Dawley rats (SPRD), and in inactin anaesthetized SPRD. Proximal intratubular free flow pressures (FFP) (13.8-14.7 mm Hg) and stop-flow pressures (40.0-42.4 mm Hg) were similar in the four groups, but systemic arterial pressure was significantly lower in WKY, and significantly higher in SHR than in SPRD. The turning point (Tp) of the feedback curve was 9.87 nl/min in SHR, significantly lower than the 13.04 nl/min found in WKY. Maximum TGF pressure response was 28.6% greater in SHR than in the normotensive rats (13.3 vs. 9.5 mm Hg; p less than 0.025). The sensitivity, as estimated from the slope of the feedback curve at the Tp [f'(Tp)] was 87% greater in SHR than in WKY. There was no significant difference between these parameters in WKY and SPRD. The TGF pressure response was biphasic in the 3 groups of halothane anaesthetized rats with a steady state level reached in about 2 min after the change in late proximal microperfusion rate. In inactin anaesthetized rats the sensitivity was 41% lower than in the halothane anaesthetized control group of SPRD, the feedback response was lower, and the feedback curve was displaced to the right with the Tp at 15.9 nl/min, significantly higher than in the control group (p less than 0.001). Although the steady state level also was reached within 2 min, the clearly biphasic pattern of the pressure response was less consistent.

A study of proximal tubular compliances in normotensive and spontaneously hypertensive rats, and the effect of anaesthesia on the compliance

Proximal tubular compliance (C) was measured in free flow microperfusion experiments from the initial slope of the increase in proximal luminal pressure divided by the step input of volume flow delivered from a microperfusion pipette inserted in a downstream proximal convolution. Five groups of rats were studied: Munich Wistar (WU, n = 11) and Sprague-Dawley rats (SPRD, n = 6) anaesthetized with inactin; and SPRD (n = 11), Wistar Kyoto (WKY, n = 9), and spontaneously hypertensive rats (SHR, n = 11) anaesthetized with halothane. In the inactin groups, C was: 0.309 +/- 0.161 and 0.266 +/- 0.136 nl mm Hg-1, respectively. In the halothane groups, C was: 0.125 +/- 0.023, 0.125 +/- 0.029, and 0.119 +/- 0.0127 nl mm Hg-1, respectively. The means in the inactin groups were significantly higher than those from the halothane groups (P less than 0.001). It is concluded that the choice of anaesthetics has a profound influence on the proximal tubular compliance in the rat, and that the compliance of SHR is equal to that of normotensive rats.

Effects of halothane-nitrous oxide inhalation anesthesia and Inactin on overall renal and tubular function in Sprague-Dawley and Wistar rats

Real function, plasma renin concentration (PRC) and prostaglandin (PG) excretion rate was studied in groups of Sprague-Dawley (SPRD) and Wistar (WIST) rats anesthetized with either Halothane-N2O or Inactin. Conscious rats were used as controls. A. In Halothane-N2O anesthesia inulin clearance (CIN) and absolute proximal reabsorption rate (APR) was moderately decreased (by about 20%), while renal plasma flow (RPF), urine flow and solute excretion remained unchanged as compared to conscious rats. There was a linear relationship between the reciprocal of the proximal occlusion time (OT) and CIN in Halothane anesthesia indicating that the proximal luminal diameter was constant and independent of CIN. B. Inactin anesthesia CIN was similarly reduced but APR was more depressed (by about 35%). RPF and solute excretion rate decreased only in SPRD rats, while urine flow was significantly reduced in both strains. 1/OT was invariant to changes in CIN indicating luminal diameter variations in proportion to CIN. Urinary PGE2-and PGF2 alpha excretion rates and PRC were moderately elevated in operated animals of both strains regardless of the anesthetics used. It is concluded that renal functional parameters in surgically prepared rats are more severely depressed by Inactin than by Halothane-N2O anesthesia. The gas anesthesia is equally well tolerated by both strains of rats.

Inactin concentration in plasma of rats during anaesthesia and the effect of this concentration on short circuit current of isolated frog skin

Inactin, given to rats for anaesthesia at a dose of 100 mg per kg body weight results in an arterial plasma concentration of 10.6 +/- 1.14 mg%, measured 40 min after the onset of anaesthesia. When similar concentrations of Inactin or Amytal were applied to frog skins the decrease in the in vitro short circuit current is dose dependent. With Inactin, the inhibition was, at least in part, reversible and the electrical conductance was not affected. Amytal however was found to depress SCC and electrical conductance irreversibly. The data are discussed in regard to active renal transport processes.