Renal effect of meclofenamate in presence and absence of superfusion bioassay

Systemic blood pressure (SBP), renal blood flow (RBF), renal vascular resistance (RVR), and arterial and renal venous prostaglandin E (PGE) concentrations were determined in pentobarbital-anesthetized dogs.The effect of sodium meclofenamate infused into the renal artery was compared under two sets of conditions. In experiments carried out under control conditions, SBP, RBF, and RVR were stable and meclofenamate caused only a slight decrease in RBF (5.4%) and increase in RVR.

Effect of [Sar1, Ala8]angiotensin II on renal vascular resistance

Partial occlusion of the renal artery (RAO) was induced in dogs anesthetized with pentobarbital or morphine chloralose-urethan. The effect of [Sar1, Ala8]angiotensin II (P-113) was compared before and during RAO on blood flow and vascular resistance of the contralateral kidney. An increase in renin secretion rate was obtained in the ischemic kidney, which was accompanied by an increase in renal vascular resistance (RVR) in the contralateral kidney and a rise in systemic blood pressure. P-113 given intra-arterially to the contralateral kidney consistently increased renal blood flow and decreased RVR during RAO, but did not alter RVR significantly before RAO. The elevation in renin secretion rate decreased between 30 and 122 min after the initiation of RAO in the pentobarbital-anesthetized dogs but not in the chloralose-urethan-anesthetized dogs. These experiments indicate that during RAO release of renin causes, through formation of angiotensin, an increase in RVR in the contralateral kidney and intra-arterial administration of P-113 restores the vascular resistance to a near-normal level.

Influence of the renin-angiotensin system on the effect of prostaglandin synthesis inhibitors in the renal vasculature

The effect of meclofenamate and indomethacin on renal blood flow and renal vascular resistance was determined under basal experimental conditions and during renal ischemia in pentobarbital-anesthetized dogs. Renal blood flow was measured with an electromagnetic flowmeter and renal arterial pressure was recorded from a catheter in the renal artery. Intra-arterial infusion of indomethacin or meclofenamate in concentrations of 4 and 4 to 8 mu-g/ml, respectively, did not cause any significant change in renal blood flow or renal vascular resistance under basal conditions. During the period of ischemia (50% reduction in renal blood flow), 4 mu-g/ml of either prostaglandin synthetase inhibitor caused a marked increase in renal vascular resistance. Prostaglandin E in the renal venous blood was decreased at the time renal vascular resistance was increased by meclofenamate. The renal vasoconstrictor response to angiotensin II injected intravenously was potentiated by both inhibitors under basal as well as ischemic conditions, which also suggested that prostaglandin synthesis was inhibited. The angiotensin antagonist 1-sar-8-ala-angiotensin II was infused intra-arterially in concentrations of 20 and 40 mmu-g/ml during renal ischemia. Subsequent administration of meclofenamate increased renal vascular resistance only slightly. The results of these experiments indicated that renal prostaglandins have more influence on renal blood flow during renal ischemia than under basal conditions, and that the renin-angiotensin system may be involved in activating synthesis and release of prostaglandins during ischemia.

Enhancement of the post-occlusive oscillation in the splenic circulation by adenosine

1. The blood flow to the splenic artery of dogs anaesthetized with sodium pentobarbitone was measured under constant pressure perfusion with the animal's own blood led from the femoral artery.2. Immediately after release of occlusion there was a rapid increase of inflow rate above the pre-occlusion level which then oscillated up and down. In a majority of cases such oscillatory responses continued for a while but progressively diminished during a period of about 6 min.3. This post-occlusive oscillatory response was not modified by either neural or autonomic receptor blocking agents such as tetrodotoxin, guanethidine, phentolamine, propranolol, atropine and methysergide.4. In the cases with a relatively short-lasting response, the selective administration of adenosine into the splenic artery caused a distinct enhancement of the oscillation.5. These results suggest that adenosine may play an important role in the post-occlusive oscillatory response of the splenic circulation.