Modulatory effects of static magnetic fields on blood pressure in rabbits.
Acute effects of locally applied static magnetic fields (SMF) on pharmacologically altered blood pressure (BP) in a central artery of the ear lobe of a conscious rabbit were evaluated. Hypotensive and vasodilator actions were induced by a Ca(2+) channel blocker, nicardipine (NIC). Hypertensive and vasoconstrictive actions were induced by a nitric oxide synthase (NOS) inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME). The hemodynamic changes in the artery exposed to SMF were measured continuously and analyzed by penetrating microphotoelectric plethysmography (MPPG). Concurrently, BP changes in a central artery contralateral to that of the exposed ear lobe were monitored. SMF intensity was 1 mT and the duration of exposure was 30 min. A total of 180 experimental trials were carried out in 34 healthy adult male rabbits weighing 2.6-3.8 kg. Six experimental procedures were chosen at random: (1) sham exposure without pharmacological treatment; (2) SMF exposure alone; (3) decreased BP induced by a single intravenous (iv) bolus injection of NIC (100 microM/kg) without SMF exposure; (4) decreased BP induced by injection of NIC with SMF exposure; (5) increased BP induced by a constant iv infusion of L-NAME (10 mM/kg/h) without SMF exposure; (6) increased BP induced by infusion of L-NAME with SMF exposure. The results demonstrated that SMF significantly reduced the vasodilatation with enhanced vasomotion and antagonized the reduction of BP via NIC-blocked Ca(2+) channels in vascular smooth muscle cells. In addition, SMF significantly attenuated the vasoconstriction and suppressed the elevation of BP via NOS inhibition in vascular endothelial cells and/or central nervous system neurons. These results suggest that these modulatory effects of SMF on BP might, in part, involve a feedback control system for alteration in NOS activity in conjunction with modulation of Ca(2+) dynamics.
Okano
H
H
Department of Physiological Hygiene, National Institute of Public Health, Tokyo, Japan. okano@iph.go.jp
Ohkubo
C
C
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D001794:Blood Pressure / Q000187:drug effects / Q000528:radiation effects*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D008280:Magnetics; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009529:Nicardipine / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010991:Plethysmography; D011817:Rabbits; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects
D002121:Calcium Channel Blockers; D009529:Nicardipine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester