ABSTRACT
In may countries, including Brazil, extracts of Jatrophona elliptica species are currently used for the treatment of several diseases. Recently it was shown that a purified compound from these plants inhibits contraction of smooth and cardiac muscle in the uM range, probably involving alterations membrane Ca2+ permeability and/or internal Ca2+ distribution. In the collagenase-isolated rat islets and in the absence of glucose, basal insulin secretion measured by radioimmunoassay averaged 122 ñ 13 uU/islet per 90 min (N=27). Jatrophone (1-100 uM/l) caused a dose-related inhibition of glucose-induced insulin release, over basal secretion, with an ID50 close to 8 uM/l. Complete inhibition of insulin release was obtained with 100 uM/l Jatrophone. However, at 100 uM/l (but not at 10 uM/l) concentration, Jatrophone also provoked a reduction in glucose metabolism by the islets which could explain, at least in part, the reduction in insulin secretion. After 120-min incubation,. the glucose metabolism, measured by the 14CO2 production, was reduced from 26.58 ñ 3.63 (N=42) to 7.48 ñ 1.36 (N=16) pmol/l per islet. In conclusion at lower concentrations (10 uM/l) Jatrophone could be a valuable tool for the study of the mechanism of insulin release induced either by glucose or other secretagogues