Role of the Submandibular Glands in In Vivo Mechanisms of Plasma Inactive Renin Release in the Rat

Abstract

In our present studies, we evaluated the role of the submandibular glands (SMG) on plasma inactive renin (PIR) releasing mechanisms in rats using some agents which are known to stimulate plasma active renin (PAR) release. The results were analyzed between sialoadenectomized (SX) and sham-operated (control: C) rats. Twenty-four h after the operation, PAR releasing agents, furosemide (FRO) 2.5 mg/rat/h with prior iv bolus 5 mg, captopril (CAP) 5 mg/rat/h with prior iv bolus 10 mg, 1-Sar-8-Ile-angiotensin II (Ang II A) 300 ng/kg/min, prostaglandin E1 (PGE1) 100 ng/kg/min, and prostaglandin I2 (PGI2) 100 ng/kg/min, were infused through femoral venous cannulae. Blood samples were taken through femoral arterial cannulae into test tubes containing 2 mg EDTA-2Na. PAR was assayed by RIA, and total renin was obtained after tryptic activation. According to the responses of PIR, the agents used were categorized into three patterns: FRO increased PIR, both PGs lowered PIR, and, CAP and Ang II A had no effect on PIR release. The PIR release mechanisms by FRO were further investigated by 20 mg FRO ip injection in totally nephrectomized rats. PIR increased even in nephrectomized rats, but the increase was totally canceled by the following SX. In conclusion, FRO alone among some agents studied is able to stimulate PIR release only under the existence of SMG.