Premium
INCREASED CA 2+ INFLUX IN THE RESTING STATE MAINTAIN THE MYOGENIC TONE AND ACTIVATES CHARYBDOTOXIN‐SENSITIVE K + CHANNELS IN FEMORAL ARTERIES FROM YOUNG SHR
Author(s) -
Asano M.,
Nomura Y.,
Hayakawa M.,
Ito K. M.,
Ito K.,
Uyama Y.,
Imaizumi Y.,
Watanabe M.
Publication year - 1995
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1995.tb02892.x
Subject(s) - charybdotoxin , nifedipine , medicine , endocrinology , chemistry , contraction (grammar) , potassium channel , tetraethylammonium , femoral artery , calcium , potassium , organic chemistry
Summary 1. To determine the possible role of voltage‐dependent Ca 2+ channels (VDCC) and Ca 2+ ‐activated K + (K Ca ) channels in the regulation of resting tone of arteries from young spontaneously hypertensive rats (SHR), mechanical responses to the agents which interact with these channels were examined in endothelium‐denuded strips of femoral arteries from 4 week old SHR and age‐matched normotensive Wistar‐Kyoto (WKY) rats. Systolic blood pressures at this age were not significantly different between SHR and WKY. 2. The strips from SHR, but not from WKY, maintained a myogenic tone; that is, the resting tone decreased when nifedipine was added. 3. Studies using 1 or 5 min pulse labelling of the strips with 45 Ca showed that the basal Ca 2+ influx was increased in SHR when compared with WKY, and this increase in SHR was abolished by nifedipine. Similar results were obtained when the cytoplasmic Ca 2+ concentration ([Ca 2+ ] i ) in the resting state of the strips was measured by fura‐PE3. 4. The addition of charybdotoxin (ChTX, a blocker of large conductance K ca channels) to the resting state caused a concentration‐dependent contraction, which was much greater in SHR than in WKY. The ChTX‐induced contraction in SHR was abolished by nifedipine. 5. In strips preloaded with 86 Rb, the basal 86 Rb efflux rate constant was significantly greater in SHR than in WKY. The increase in 86 Rb efflux in SHR was abolished by nifedipine. 6. The results suggest that the Ca 2+ influx via L‐type VDCC was increased in the resting state of the femoral artery from 4 week old SHR, and therefore the myogenic tone was maintained and ChTX‐sensitive K + channels were highly activated.