Enhanced depressor effect of centrally administered high-calcium solution in salt-loaded experimental hypertension.
The depressor effect by oral calcium supplementation is known to be more pronounced in salt-dependent than in renin-dependent hypertension. This study was conducted to investigate the role of central calcium on two different pathophysiologic subtypes of experimental hypertension; (a) salt-dependent, deoxycorticosterone acetate-salt hypertensive rats (DOCA), and (b) renin-dependent, 2-kidney, 1 clip (2-K, 1C) hypertensive rats. In DOCA (n = 10), high-calcium solution (Ca+2, 65.2 mM, 10 microl) given centrally (i.c.v.) elicited a marked decrease in mean blood pressure (MBP; 170 +/- 4 to 138 +/- 5 mm Hg, p < 0.01) with a decrease in heart rate (HR; 390 +/- 18 to 344 +/- 17 beats/min, p < 0.05) lasting for 40 min. In 2-K, 1C (n = 10), high-Ca2+ i.c.v. showed a lesser decrease in MBP (178 +/- 4 to 171 +/- 5 mm Hg) and HR (419 +/- 10 to 395 +/- 12 beats/min) with shorter duration (for 20 min) than in DOCA. This significant depressor and bradycardic response to Ca2+ i.c.v. observed in DOCA was dose dependent at Ca2+ concentrations between 65.2 and 130.4 mM. In DOCA, high Ca2+ i.c.v. reduced the plasma noradrenaline (Nad) concentration significantly (479 +/- 81 to 319 +/- 62 pg/ml, p < 0.05). These results suggest that central Ca2+ plays a more important role in regulating sympathetic nerve activity and BP in salt-dependent than in renin-dependent experimental hypertension.
Ozeki
S
S
Third Department of Internal Medicine, Nagasaki University School of Medicine, Sakamoto, Japan.
Seto
S
S
Nagao
S
S
Kusano
S
S
Kitamura
S
S
Oda
S
S
Akahoshi
M
M
Yano
K
K
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000008:administration & dosage / Q000494:pharmacology*; D003900:Desoxycorticosterone / Q000009:adverse effects; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000139:chemically induced / Q000503:physiopathology*; D007276:Injections, Intraventricular; D008297:Male; D009638:Norepinephrine / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D012083:Renin / Q000502:physiology; D012965:Sodium Chloride / Q000009:adverse effects
D003900:Desoxycorticosterone; D012965:Sodium Chloride; D012083:Renin; D002118:Calcium; D009638:Norepinephrine