RESUMEN
Aim To study the electrophysiological mechanism of dopamine inhibiting insulin secretion hv voltage-dependent potassium ( Kv) channels.Methods Islets and (3 cells were isolated from male SD rats.D,-like receptor agonist ( SKP38393), D2-like receptor agonist (Quinpirole) and antagonist (Epiclopride) were used according to the experiment.Insulin secretion was detected by insulin radioimmunoassay.Whole-cell j J patch-clamp technique was applied to detect Kv channel currents and action potential duration of p cells.Di- BAC4(3) staining was used to observe membrane potential.Results SKF38393 did not affect insulin secretion and the Kv channel currents.Quinpirole signifi cantly inhibited insulin secretion and increased Kv channel currents.Dopamine significantly inhibited insulin secretion, increased Kv channel currents and shortened action potential duration of p cells, which could be reversed by epiclopride.In addition, dopamine de-creased membrane potential of INS-1 cells.Conclusions Dopamine inhibits insulin secretion by acting on D2-like receptors, resulting in actived Kv channels, shortened action potential duration and decreased cell membrane potential.
RESUMEN
The rat everted intestinal sac model was adopted to investigate the absorption of total flavonoids from Coreopsis tinctoria in different intestinal segments. Cyaniding-3-O-β-D-glucoside, chlorogenic acid, flavanomarein, quercetagetin-7-O-β-D-glucoside, iso-okanin, marein and 3,5-dicaffeoylquinic acid which as the major chemical components of total flavonoids from C. tinctoria were selec-ted as the study objects to evaluate the absorption characteristics of each component in different intestinal segments. The results showed that the absorption of seven components of total flavonoids at different intestinal segments was in consistent with zero order absorption rate. The K_a of chlorogenic acid, flavanomarein, quercetagetin-7-O-β-D-glucoside, isookanin and 3,5-dicaffeoylquinic acid increased with increasing of concentration of total flavonoids(P<0.05), indicating that the intestinal absorption of these five components was passive transport. The K_a of cyaniding-3-O-β-D-glucoside and marein showed a weak concentration dependence, suggesting that the absorption of them may be an positive and passive co-existing mode. The result of absorption in different intestinal segments showed that cyaniding-3-O-β-D-glucoside, chlorogenic acid, flavanomarein, quercetagetin-7-O-β-D-glucoside, marein and 3,5-dicaffeoylquinic acid were mainly absorbed in ileum, while isookanin was mainly absorbed in jejunum. The total flavonoids of C. tinctoria are selectively absorbed in intestinal tract, the rat everted intestinal sac model can be used to evaluate the multi-component intestinal absorption characteristics of total flavonoids from C. tinctoria.