Involvement of voltage-sensitive calcium ion channels in release of luteinizing hormone-releasing hormone from the bovine infundibulum /
Bovine infundibular explants (INFE) were cultured to confirm calcium (Ca.) and voltage-sensitive calcium channel (VSCC) involvement in luteinizing hormone-releasing hormone (LHRH) release. Mid-sagitally sectioned INFE, randomly assigned to control or treated groups, were incubated in 600 0 of Krebs...
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| Format: | Thesis eBook |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1993.
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| Online Access: | Link to OAKTrust copy |
| Summary: | Bovine infundibular explants (INFE) were cultured to confirm calcium (Ca.) and voltage-sensitive calcium channel (VSCC) involvement in luteinizing hormone-releasing hormone (LHRH) release. Mid-sagitally sectioned INFE, randomly assigned to control or treated groups, were incubated in 600 0 of Krebs-Ringer bicarbonate medium (KRB) (pH 7.2,371 C, saturated with 95% 02,5% C02) for 180 min. At 30 min intervals, 500 0 aliquots were removed from each incubate and replaced with fresh media. Basal (BAS) and depolarization induced (DEPI) (60 mM K+) LHRH release were evaluated by RIA of LHRH content in the media at 90-120 and 120-150 min of culture, respectively. INFE from steers treated with 1.25 mM EGTA (Ca binding agent) in the KRB released less (p<.001) LHRH during depolarization than controls; thus, confirming Ca involvement in LHRH release. INFE from steers treated with 50 or 100 pM verapamil (a phenylalkylamine-type Ca L channel blocker) in the KRB released less (p<.09), (p<.0001), respectively, LHRH in response to depolarization than controls. Likewise, INFE from heifers treated with 50 or 100 pM verapamil in the KRB released less (p<.05) LHRH in response to depolarization than controls. On the other hand, INFE from steers treated with 5, 50, or 1 00 pM nifedipine (a dihydropyridine-type Ca L channel blocker) or heifers treated with 5, 200, or 500 pM nifedipine in the KRB did not differ in the amount of LHRH released in response to depolarization than controls. INFE from steers treated with 10 or 1000 liM Bay K 8644 (a dihydropryidinetype L Ca channel agonist) or heifers treated with 10 pM Bay K 8644 in the KRB did not differ in the amount of LHRH released as compared to the controls. These results support involvement of extracellular Ca in DEPI LHRH release (exocytosis) from the bovine INFE and suggest Ca entry is mediated through L-type VSCC. The results also suggest that the dominant binding sites of the L-type channels associated with DEPI LHRH release are more sensitive to the phenylalkylamines than the dihydropryidines. |
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| Item Description: | "Major Subject: Physiology of Reproduction". Vita. |
| Physical Description: | x, 86 leaves : illustrations ; 28 cm. Also available online. |
| Bibliography: | Includes bibliographical references. |