Effects of angiotensin II and noradrenaline on intrarenal haemodynamics in the rat

Pressor and intra-renal effects of angiotensins I and II, and noradrenaline, in anaesthetized and conscious sheep

The pressor and intra-renal actions and effects of octa - and deca-peptides angiotensins II and I and of the catecholamine noradrenaline, in anaesthetized and conscious sheep, are considered. The halothane anaesthetic substantially lowers pressor sensitivity to both peptides but does not influence their ability to liberate K(+) ions into the circulating plasma. In comparison with angiotensin II, both angiotensin I and noradrenaline -- with direct presentation to the kidney -- are ineffective in decreasing intra-renal blood flow. However, with left ventricular injection, both pressor compounds immediately increase the blood pressure, as does angiotensin II. Combined doses of the decapeptide and catecholamine are thus highly effective in raising the blood pressure while having a minimal effect on blood flow through the kidney. This overall situation could provide a basis for treating clinical shock, especially regarding septicaemia and septic shock. The lowered hind-limb blood flow, with administration of the pressor compounds into the femoral artery, contrasts strongly with the raised flow resulting from intravenous injection. Experimental procedures to establish, or otherwise, relevant hypothetical situations are detailed.

Validation of transonic small animal flowmeter for measurement of cardiac output and regional blood flow in the rat

The objective of the present study was to validate a transonic flowmeter system with two probes (model 3SS for cardiac output (CO) and 1RB for organ flows) in Sprague-Dawley (SD) rats first by measuring blood flow through pump-infused isolated renal artery and ascending aorta, and then through measurements of CO and renal, mesenteric, and hindquarter blood flow (RBF, MBF, HBF) in vivo. We measured in vivo baseline flow and changes in flow induced by dopamine and propranolol for CO, prostaglandin E2 (PGE2), and angiotensin II (AII) for RBF and pentobarbital sodium for MBF and HBF. Correlations between meter and pump flow were linear (r = 0.999, p < 0.001) with close agreement both in ascending aorta and renal artery flow measurements. The baseline values were 15 +/- 0.7 ml/100 g/min for CO, 4 +/- 0.1 ml/100 g/min for RBF, 7 +/- 0.3 ml/100 g/min for MBF, and 6 +/- 0.3 ml/100 g/min for HBF, respectively. The system reliably detected increase and/or decrease in CO and regional blood flows. The transonic flowmeter system is accurate, highly reproducible, and compatible with other established techniques for measuring CO and regional blood flows in the rat.

Increased therapeutic effect on metastatic liver tumors in rats of two-route chemotherapy using cis-diamminedichloroplatinum (II) and its antidote, sodium thiosulfate, with temporary clamping of the abdominal aorta

To improve the therapeutic effects of conventional "two-route chemotherapy" (TRC) comprising cis-diamminedichloroplatinum(II) (CDDP) given via the hepatic artery plus simultaneous i.v. sodium thiosulfate (STS) on metastatic liver tumors in rats, we combined TRC with aortic clamping at the supraceliac level. Treatments were evaluated in Wistar-King-Aptekman (WKA) rats bearing metastatic liver tumors 7 days after the inoculation of 10(6) syngenic RBT-1 (transitional-cell carcinoma) cells via the mesenteric vein. When 15 mg/kg CDDP was injected i.a. over 5 min, immediately followed by STS 1,580 mg/kg (200-fold the molar equivalent of 15 mg/kg CDDP) given i.v. over a further 5 min, the antitumor activity, evaluated by the number of tumor nodules present 12 days after treatment, was superior to that of conventional TRC (15 mg/kg i.a. CDDP plus simultaneous administration of 1,580 mg/kg i.v. STS), but the blood urea nitrogen (BUN) level was highly elevated (63.6 mg/dl). With aortic clamping for 7.5 min during CDDP administration and the first half of STS treatment, the TRC consisting of CDDP plus delayed STS (modified TRC) exhibited a further improvement in antitumor activity, with no nephrotoxicity (BUN, 17.1 mg/dl). Although the antitumor activity of 3 or 5 mg/kg i.a. CDDP was also increased by aortic clamping, in animals with normal BUN levels the survival of those treated with modified TRC was greater than that of rodents given 3 mg/kg i.a. CDDP with aortic clamping; however, the former was the same as that of animals given 5 mg/kg i.a. CDDP with aortic clamping whose BUN levels were elevated (31.2 mg/dl). Loss of body weight, the decrease in WBC counts, and changes in the serum transaminase levels in rats given modified TRC were tolerable. The improved therapeutic effect of modified TRC can be explained as follows: during aortic clamping, (a) CDDP delivery to the kidney decreased by 96% and made feasible the delay in STS administration after CDDP without nephrotoxicity, and (b) CDDP retention in the liver was increased by 366%, as aortic clamping decreased the portal blood flow, thereby inhibiting the washout of CDDP from the liver.

Efficacy of two-route chemotherapy using cis-diamminedichloroplatinum(II) and its antidote, sodium thiosulfate, in combination with angiotensin II for rat liver tumor

To improve the therapeutic effects of conventional TRC using i.a. CDDP plus simultaneous i.v. STS in a rat liver tumor, we made use of the AT-II-induced hypertension method, in combination with TRC. The decrease in tumor area (-15%), measured 8 days after the TRC using CDDP 12 mg/kg i.a. plus i.v. post-administration (5 min later) of STS 1,264 mg/kg, was much greater than that (+ 13%) seen in the conventional TRC, but BUN level was elevated (44.9 mg/dl). AT-II (15 micrograms/kg) administered i.a. simultaneously with CDDP normalized the BUN level (20.3 mg/dl) and further decreased (-15% to -31%) the tumor area (modified TRC). The modified TRC also exhibited a higher anti-tumor effect than did CDDP 3 mg/kg with AT-II i.a. (5%) at a similar BUN level (22.2 mg/dl). Loss of body weight, decrease in WBC count and changes in serum transaminases of rats treated with the modified TRC were tolerable. The improved therapeutic effect of the modified TRC was explained as follows: during AT-II-induced hypertension, (I) CDDP delivery to the tumor was increased by 150% and (2) CDDP delivery to the kidney was decreased by 35%. The latter effect of AT-II made feasible the post-administration of STS to CDDP.

Effect of exogenous angiotensin-II on local blood flow in kidneys with neoplasm. Experiments in the rat

The effect of angiotensin-II on the local renal blood flow and arterial blood pressure was investigated in the rat with the H2 gas washout technique. Increasing intravenous infusion rates gave a decreasing blood flow and increasing blood pressure, renal vascular resistance being close to proportional to the log of infusion rate. In kidneys with experimental neoplasm, the flow reduction was proportionally less in the tumor than in intact renal tissue. The respective flow levels were maintained for 10 to 45 min without tendency to change.

Renal function and intrarenal hemodynamics in acutely hypoxic and hypercapnic rats

On the basis of microsphere distribution, inert gas washout, and standard clearance data, the effects of acute hypoxia and hypercapnia on the kidney were studied in anesthetized, mechanically ventilated rats. Moderate hypoxia (mean PO2, 48 mm Hg) did not significantly change diuresis, GFR, and tubular sodium rejection. Due to a decrease in renal vascular resistance (R) from 40.1 to 31.8 mm Hg ml-1 min, mean renal blood flow stayed constant in spite of a significant drop in mean arterial blood pressure. Hypoxic changes in R were not accompanied by significant changes in intrarenal distribution of blood flow (IDBF). In severe hypoxia (PO2 less than 45 mm Hg) with oliguria and marked arterial hypotension, R was the lowest of all groups (28.8 mm Hg ml-1 min). Hypercapnia did not significantly change the renal excretory parameters, although an increase in R (without change in IDBF), together with a decrease in MAP caused a marked drop in mean renal blood flow. From these studies we conclude: 1) in the anestheized rat, acute hypoxia caused significant changes in intrarenal hemodynamics without changes in excretory function, 2) hypoxic renal vasodilation persists even in severe hypotension with oliguria and anuria, 3) in acute hypoxia and hypercapnia, changes in renal blood flow and renal vascular resistance are not accompanied by significant changes in IDBF.