Related Experiment Videos
Calcium involvement in luteinizing hormone-releasing hormone release from the bovine infundibulum
W W Dippel1, P L Chen, N H McArthur
1Department of Animal Science, Texas A&M University, College Station 77843, USA.
Insights
Calcium is crucial for luteinizing hormone-releasing hormone (LHRH) release from bovine neurons. Blocking calcium channels or chelating calcium significantly reduced LHRH release, confirming calcium
Area of Science:
- Neuroendocrinology
- Reproductive Biology
- Calcium Signaling
Background:
- Luteinizing hormone-releasing hormone (LHRH) regulates reproduction.
- The role of calcium in LHRH release from bovine neurons is not fully understood.
Purpose of the Study:
- To investigate the involvement of calcium (Ca) in LHRH release from bovine infundibular explants.
- To test the hypothesis that Ca is essential for LHRH release from neuron terminals.
Main Methods:
- In vitro incubation of bovine infundibular explants (stalk median eminence).
- Treatment with EGTA (calcium chelator) or verapamil (L-type calcium channel antagonist).
- Measurement of spontaneous and depolarization-induced LHRH release via radioimmunoassay.
Main Results:
- EGTA treatment significantly reduced depolarization-induced LHRH release.
- Verapamil treatment also significantly decreased depolarization-induced LHRH release.
- Spontaneous LHRH release was not affected by EGTA or verapamil.
Conclusions:
- Calcium influx through L-type channels is critical for depolarization-induced LHRH release in cattle.
- EGTA and verapamil inhibit LHRH release, supporting the role of calcium in this process.
Abstract:
Bovine infundibular (stalk median eminence) explants were incubated in vitro to test the hypothesis that calcium (Ca) is involved in the release of luteinizing hormone-releasing hormone (LHRH) from LHRH neuron terminals in cattle. Right and left infundibular halves from individual heifers and/or steers were randomly assigned to either control or treated (EGTA [a Ca chelator] or verapamil [an L-type Ca channel antagonist]) groups. Each half was incubated in 600 microliters of Krebs-Ringer bicarbonate medium (KRB) in the presence or absence of a treatment agent for 180 min. At 30-min intervals, 500-microliters samples were removed from each incubated and replaced with fresh media. Spontaneous (basal) and depolarization-induced (60 mM potassium) LHRH release was evaluated by radioimmunoassay of the LHRH content in the media incubated from 91 to 120 and 121 to 150 min of culture, respectively. The effect of treatment on depolarization-induced LHRH release was analyzed by comparing the differences between spontaneous and depolarization-induced LHRH release in control and treated groups. Spontaneous LHRH release was not different between control and 1.25 mM EGTA- or 100 microM verapamil-treated halves from steers. In contrast, steer infundibular halves incubated with EGTA (replacing Ca in KRB and chelating any Ca in the media) released less LHRH during depolarization than did control halves. In addition, verapamil-treated (to block Ca uptake by the terminal) infundibular halves from steers or heifers released less LHRH in response to depolarization than did control halves.(ABSTRACT TRUNCATED AT 250 WORDS)