Presentation Title

Different Calcium Channels Mediate Basal and Stimulated MSH Secretion

Speaker Credentials

Professor

Speaker Credentials

Ph.D.

College

College of Medical Sciences, MBS

Location

Signature Grand, Davie, Florida, USA

Format

Poster

Start Date

25-4-2008 12:00 AM

End Date

25-4-2008 12:00 AM

Abstract

Objective. We investigated the types of calcium channels involved in basal and K-stimulated MSH secretion. Background. Both basal and K-stimulated secretion of melanophore-stimulating hormone (MSH) from neurointermediate lobes (NILs) of the anole are Ca dependent. Nimodipine and BAY K 8644, which block and potentiate, respectively, Ca influx through L-type Ca channels, block and potentiate, respectively, K-stimulated MSH secretion but have no effect on basal secretion. These observations suggest that K-stimulated MSH secretion is mediated by Ca influx through L-type Ca channels whereas basal secretion is not. We further investigated the Ca channels involved in both basal and K-stimulated MSH secretion using toxins which preferentially block different types of Ca channels. Methods. Anole NILs were placed in a perifusion chamber and the MSH content of the perifusate was measured using the Anolis skin bioassay. None of the toxins affected the assay. Results. sFTX-3.3 a blocker of P/Q and T-type Ca channels, inhibited basal but not K-stimulated secretion. Agatoxin, a selective P/Q-type Ca channel blocker, had no effect on either basal or K-stimulated secretion suggesting that the block of basal secretion by sFTX-3.3 was due to its effects on T-type channels. The L-type Ca channel blocker FS-2, behaved like nimodipine and suppressed K-stimulated secretion but not basal secretion. A selective N-type Ca channel blocker, ω-conotoxin GVIA, had no effect on either K-stimulated or basal secretion. Conclusion. These results indicate that basal and K-stimulated secretion are mediated by Ca influx through different Ca channels: basal through T-type and K-stimulated through L-type Ca channels. Grants. This study was supported by a NSU-HPD Research Award.

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Apr 25th, 12:00 AM Apr 25th, 12:00 AM

Different Calcium Channels Mediate Basal and Stimulated MSH Secretion

Signature Grand, Davie, Florida, USA

Objective. We investigated the types of calcium channels involved in basal and K-stimulated MSH secretion. Background. Both basal and K-stimulated secretion of melanophore-stimulating hormone (MSH) from neurointermediate lobes (NILs) of the anole are Ca dependent. Nimodipine and BAY K 8644, which block and potentiate, respectively, Ca influx through L-type Ca channels, block and potentiate, respectively, K-stimulated MSH secretion but have no effect on basal secretion. These observations suggest that K-stimulated MSH secretion is mediated by Ca influx through L-type Ca channels whereas basal secretion is not. We further investigated the Ca channels involved in both basal and K-stimulated MSH secretion using toxins which preferentially block different types of Ca channels. Methods. Anole NILs were placed in a perifusion chamber and the MSH content of the perifusate was measured using the Anolis skin bioassay. None of the toxins affected the assay. Results. sFTX-3.3 a blocker of P/Q and T-type Ca channels, inhibited basal but not K-stimulated secretion. Agatoxin, a selective P/Q-type Ca channel blocker, had no effect on either basal or K-stimulated secretion suggesting that the block of basal secretion by sFTX-3.3 was due to its effects on T-type channels. The L-type Ca channel blocker FS-2, behaved like nimodipine and suppressed K-stimulated secretion but not basal secretion. A selective N-type Ca channel blocker, ω-conotoxin GVIA, had no effect on either K-stimulated or basal secretion. Conclusion. These results indicate that basal and K-stimulated secretion are mediated by Ca influx through different Ca channels: basal through T-type and K-stimulated through L-type Ca channels. Grants. This study was supported by a NSU-HPD Research Award.