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Role of Ca + ‐dependent K‐channels in the membrane potential and contractility of aorta from spontaneously hypertensive rats
Author(s) -
Silva Eneida G.,
FredianiNeto Eugenio,
Ferreira Alice T.,
Paiva Antonio CM.,
Paiva Therezinha B.
Publication year - 1994
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1994.tb17095.x
Subject(s) - apamin , depolarization , medicine , endocrinology , tetraethylammonium , membrane potential , chemistry , hyperpolarization (physics) , aorta , spontaneously hypertensive rat , contractility , stimulation , potassium channel , potassium , biochemistry , blood pressure , organic chemistry , nuclear magnetic resonance spectroscopy
1 Contractile responses to KCl and membrane potentials were determined in aortic rings from spontaneously hypertensive rats (SHR), normotensive Wistar rats (NWR) and Wistar Kyoto rats (WKY) both in the absence and in the presence of the Ca 2+ ‐dependent K‐channel blockers, apamin and tetraethylammonium (TEA). 2 Compared to NWR, aortic rings from WKY and SHR were less reactive and their Ca 2+ uptake after stimulation with K + was decreased. 3 Smooth muscle cell membrane potentials were higher in aortae from SHR and WKY than in NWR aortae, whereas SHR had higher K + and lower Na + intracellular activities than WKY and NWR, suggesting overactivity of the Na + /K + pump in the hypertensive animals. 4 Treatment with apamin caused depolarization of WKY and SHR aortae, and increased their contractile responses to the same level as those of the NWR. Treatment with TEA also caused depolarization of aortae from WKY and SHR, but in the SHR the depolarization induced by TEA was smaller than that produced by apamin and the contractile responses to KCl did not reach the level of those of aortae from NWR. 5 It is concluded that overactivity of Ca 2+ ‐dependent K‐channels in aortae of WKY and SHR contributes to their higher membrane potentials and lower responsiveness to vasoconstrictor stimuli. In SHR, an overactive Na + /K + pump is also present, and the contribution of apamin‐sensitive Ca 2+ ‐dependent K‐channels to the membrane potential and reactivity appears to be more relevant than that of TEA‐sensitive channels.