Involvement of protein kinase C and intracellular Ca2+ in goldfish brain somatostatin-28 inhibitory action on growth hormone release in goldfish

Three Native Somatostatin Isoforms Differentially Affect Membrane Voltage-Sensitive Ion Currents in Goldfish Somatotrophs

“…5 and Table 2). Using an identical protocol, 10 n m gbSS‐28 was also shown to suppress basal GH release reversibly in a previous study (28).…”

“…Because basal GH release in goldfish somatotrophs is dependent on extracellular Ca 2+ and dihydropyridine‐sensitive VSCCs (31, 32), SS‐induced increases in I Kv and decreases in Ca 2+ currents and the associated decrease in membrane excitability would be expected to suppress basal [Ca 2+ ] i in conjunction with GH release in these cells. In previous studies, SS‐14 was reported to cause a small but insignificant decrease in basal [Ca 2+ ] i ; on the other hand, gbSS‐28 reduced basal [Ca 2+ ] i levels significantly by approximately 29% (28, 50). In the present study, both 0.1 μ m SS‐14 and [Pro 2 ]SS‐14 significantly decreased basal [Ca 2+ ] i , by 11–13%.…”

“…†Significantly different from duration of SS application of 300 s (P < 0.05). ‡Data on gbSS‐28 are obtained from experiments reported by Yu and Chang (28).…”

“…Previous results indicate that, after the removal of gbSS‐28, a rebound increase in [Ca 2+ ] i and GH release, such as would be expected with SS‐14 action in mammalian somatotrophs, is not observed (28). In the present study, although a small but clear rebound of [Ca 2+ ] i occurs upon termination of SS‐14 or [Pro 2 ]SS‐14 treatments exists (Fig.…”

“…Following overnight culture on poly‐ l ‐lysine‐coated coverslips, pituitary cells were loaded with Fura‐2/AM (10 μ m ) for 35–40 min according to established protocols (28). Using Series 20 closed bath imaging chamber (260 μl bath volume; Warner Instruments, Hamden, CT, USA), the cells were perifused at a flow rate of 1 ml/min at 18–20 °C.…”