Pituitary control of BK potassium channel function and intrinsic firing properties of adrenal chromaffin cells.
The discovery that the hypothalamic-pituitary-adrenocortical (HPA) endocrine stress axis controls an alternative splicing decision in chromaffin Slo-encoded BK (big potassium) channels raised the possibility that activation of the HPA could serve as a mechanism to tune the intrinsic electrical properties of epinephrine-secreting adrenal chromaffin cells. To test this, we compared BK functional properties and cell excitability in chromaffin cells from normal and hypophysectomized (pituitary-ablated) rats. Hypophysectomy was found to alter the voltage dependence and kinetics of BK gating, making channels less accessible for activation from rest. Perforated-patch recordings revealed changes in action potential waveform and repetitive firing properties. The maximum number of spikes that could be elicited with a 2 sec depolarizing current pulse was reduced by approximately 50% by hypophysectomy. The results indicate that pituitary hormones can adapt the mechanics of adrenal catecholamine release by tailoring BK channel function.
Lovell
P V
PV
Department of Neurobiology and Behavior, Cornell University, Ithaca, New York 14853, USA.
McCobb
D P
DP
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D017398:Alternative Splicing; D000818:Animals; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D003198:Computer Simulation; D004558:Electric Stimulation; D007016:Hypophysectomy; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D008954:Models, Biological; D018408:Patch-Clamp Techniques; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism* / Q000601:surgery; D010907:Pituitary Hormones / Q000378:metabolism / Q000494:pharmacology; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D024681:Potassium Channels, Calcium-Activated; D051381:Rats; D017207:Rats, Sprague-Dawley
C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D051036:Large-Conductance Calcium-Activated Potassium Channels; D010907:Pituitary Hormones; D015221:Potassium Channels; D024681:Potassium Channels, Calcium-Activated