Adrenomedullin enhances glucose toxicity to pancreatic beta-cell of islets from spontaneously hypertensive rat (SHR) / 生物医学工程学杂志

ABSTRACT

This animal experiment was aimed at the questions whether high glucose concentration inhibits insulin secretion (glucose toxicity, GT) of beta-cell of islets from SHR and Wistar-Kyoto (WKY) rat and whether adrenomedullin (AM) enhances GT. Ten 6-week-old SHRs (test group) and ten 10-week-old Wistar-Kyoto rats (WKY) (control group) were selected. RAMI-1640 medium containing 5.6 mM glucose (normal glucose group) and 20 mM glucose (high glucose group) were applied. Various concentrations of AM (0, 10(-8), 10(-7), 10(-6) M) and RPMI-1640 medium containing high glucose were mixed, respectively. The isolated islets from rats were put into 12-well plates (90 islets/well). The islets were incubated in RAMI-1640 medium containing normal or high glucose for one hour. Then the supernatants from both incubations were determined by RIA for insulin. In SHR group, the insulin concentration in supernatants gained from high glucose group without AM was lower than that from normal glucose group (19.9+/-6.6 vs 60.9+/-33.6 mU/L, P<0.05). With the increment of the concentration of AM, insulin concentration in supernatants from islets incubated in high glucose and various concentrations of AM tended to be low further (19.9+/-6.6 vs 22.2+/-8.0 vs 21.5+/-5.6 vs 17.9+/-3.6 mU/L). The changing tendency in control group was the same as in SHR group. When the islets were incubated in normal glucose and high glucose medium, the insulin concentration in supernatant significantly decreased in SHR group compared with that in control group (P<0.01). The insulin secretion was inhibited by high glucose in beta-cell of islets from SHR and WKY. The results suggest GT to beta-cell of islets from SHR and WKY. AM tended to inhibit insulin secretion in a dose-dependent manner in beta-cell of islets from SHR and WKY. The inhibition of insulin secretion caused by high glucose in beta-cell of islets from SHR was more remarkable than from WKY. This may be related to secretion dysfunction in beta-cell of islets from SHR.