Augmented central pressor action of magnesium in SHR.
This study attempted to determine whether central magnesium (Mg) influences the regulation of blood pressure (BP). An intracerebroventricular (icv) injection of a high Mg2+ solution (190.0 mEq/L, 10 microL), made by adding MgC12 to artificial cerebrospinal fluid, increased the mean BP in both conscious spontaneously hypertensive rats (SHR; n = 17, p < 0.001) and Wistar Kyoto rats (WKY; n = 8, p < 0.005). Spontaneously hypertensive rats showed a greater pressor response than WKY (+11.7 +/- 0.9 mm Hg versus +3.5 +/- 1.1 mm Hg, p < 0.001). This pressor response to Mg2+ given icv was dose-dependent in the range of Mg2+ concentration between 47.5 and 190.0 mEq/L in SHR. A high Mg2+ solution (190.0 mEq/L), made by adding MgSO4 given icv, also increased the mean BP in SHR (n = 7, p < 0.001) and WKY (n = 6, p < 0.01), whereas the high osmolarity solution (340 mOsm/kg H2O) given icv did not change the mean BP in either SHR or WKY. Also administered was a high Mg2+ solution icv after either hexamethonium bromide (Hx; 50 mg/kg intravenously) or arginine vasopressin antagonist (aAVP, (CH2)5Tyr(Me)AVP, 30 micrograms/kg i.v.). The pressor response to the high Mg2+ solution was abolished by arginine vasopressin antagonist both in SHR and WKY, although it was not canceled by Hx. A high Mg2+ solution administered icv caused a 3.5-fold increase in plasma arginine vasopressin concentration in SHR (n = 5, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
Oda
S
S
Third Department of Internal Medicine, Nagasaki University School of Medicine, Japan.
Seto
S
S
Akahoshi
M
M
Nagao
S
S
Ozeki
S
S
Kusano
S
S
Yano
K
K
Hashiba
K
K
D000818:Animals; D001127:Arginine Vasopressin / Q000037:antagonists & inhibitors / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006973:Hypertension / Q000503:physiopathology*; D007276:Injections, Intraventricular; D008274:Magnesium / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013564:Sympathetic Nervous System / Q000503:physiopathology
D001127:Arginine Vasopressin; D008274:Magnesium