Comparison of Ca2+ currents of chromaffin cells from normotensive Wistar Kyoto and spontaneously hypertensive rats.
Spontaneously hypertensive rats (SHR) are widely used as model to investigate the pathophysiological mechanisms of essential hypertension. Catecholamine plasma levels are elevated in SHR, suggesting alterations of the sympathoadrenal axis. The residual hypertension in sympathectomized SHR is reduced after demedullation, suggesting a dysfunction of the adrenal medulla. Intact adrenal glands exposed to acetylcholine or high K+ release more catecholamine in SHR than in normotensive Wistar Kyoto (WKY) rats, and adrenal chromaffin cells (CCs) from SHR secrete more catecholamines than CCs from WKY rats. Since Ca2+ entry through voltage-gated Ca2+ channels (VGCC) triggers exocytosis, alterations in the functional properties of these channels might underlie the enhanced catecholamine release in SHR. This study compares the electrophysiological properties of VGCC from CCs in acute adrenal slices from WKY rats and SHR at an early stage of hypertension. No significant differences were found in the macroscopic Ca2+ currents (current density, I–V curve, voltage dependence of activation and inactivation, kinetics) between CCs of SHR and WKY rats, suggesting that Ca2+ entry through VGCC is not significantly different between these strains, at least at early stages of hypertension. Ca2+ buffering, sequestration and extrusion mechanisms, as well as Ca2+ release from intracellular stores, must now be evaluated to determine if alterations in their function can explain the enhanced catecholamine secretion reported in CCs from SHR.
División de Neurociencias, Departamento de Neurociencia Cognitiva, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito de Investigación Científica s/n, Ciudad Universitaria, CP 04510, Mexico City, DF, Mexico.
Pedro
P
Segura-Chama
Adán
A
Hernández
Nicolás
N
Jiménez-Pérez
Tzitzitlini
T
Alejandre-García
Claudia V
CV
Rivera-Cerecedo
Jesús
J
Hernández-Guijo
Arturo
A
Hernández-Cruz
D000818:Animals; D019898:Autocrine Communication / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D015220:Calcium Channels / Q000378:metabolism*; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects; D008297:Male; D009532:Nickel / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D015220:Calcium Channels; D009532:Nickel; D009543:Nifedipine