The effect of theophylline and cyclic adenosine 3,5-monophosphate on renin release by afferent arterioles

Abstract

The effects of theophylline and cyclic adenosine 3',5'-monophosphate (cAMP) on renin release by afferent arterioles were studied. Rabbit afferent arterioles (seven to 10), obtained by a microdissection technique, were incubated for three consecutive 20 min periods in 100 microliters of Medium 199 with 0.1% bovine serum albumin (BSA). Afferent arterioles exposed to theophylline, 1 x 10(-4) mol/l, produced a greater than 100% increase in renin release (0.18 +/- 0.04 to 0.42 +/- 0.05 ng angiotensin l/h per arteriole per h incubation). The renin release stimulated by theophylline was completely abolished by indomethacin and meclofenamate. The stimulation of renin secretion was also blocked when extracellular calcium concentration was decreased to 10(-7) mol/l and the arterioles were permeabilized with calcium ionophore. Dibutyryl cAMP (db-cAMP), 1 x 10(-4) mol/l, and forskolin, 1 mumol/l or 100 mumol/l, failed to stimulate renin release by afferent arterioles. The results of this study therefore suggest that theophylline-stimulated renin release may be mediated through a prostaglandin pathway. The stimulation of renin secretion is also dependent on the extracellular concentration of calcium.