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Title: Hypothyroid state reduces calcium channel function in 18-day pregnant rat uterus
Authors: Parija, S C
Mishra, S K
Raviprakash, V
Keywords: Calcium
Issue Date: Jan-2006
Publisher: CSIR
Abstract: Hypothyroidism significantly reduced the mean amplitude and increased the mean frequency of spontaneous rhythmic contractions in 18day pregnant rat uterus. Nifedipine (10-12-10-9 M) and diltiazem (10-10-10-6M) caused concentration related inhibition of the myogenic responses of the uterine strips obtained from both pregnant and hypothyroid state. However, nifedipine was less potent (IC50:2.11×10-11 M) in pregnant hypothyroid state as compared to pregnant control (IC50: 3.1×10-12M). Similarly, diltiazem was less potent (IC50 : 3.72×10-9 M) in inhibiting the uterine spontaneous contractions in hypothyroid than in pregnant rat uterus (IC50:5.37×10-10 M). A similar decrease in the sensitivity to nifedipine and diltiazem for reversal of K+ (100 mM)–induced tonic contraction and K+-stimulated 45Ca2+ influx was observed with these calcium channel antagonists in uterus obtained from hypothyroid pregnant rats compared to the controls. Nifedipine–sensitive influx of 45Ca2+-stimulated either by K+ (100 mM) or by Bay K8644 (1,4-dihydro-2,6-methyl-5-nitro-4-[2'-(tri-fluromethyl)phenyl]-3-pyridine carboxylic acid methyl ester) (10-9 M) was significantly less in uterine strips from hypothyroid rats compared to controls. The results suggest that the inhibition of uterine rhythmic contractions may be attributable to a reduction in rat myometrial Ca2+ channel function in the hypothyroid state.
Page(s): 19-27
ISSN: 0975-1009 (Online); 0019-5189 (Print)
Source:IJEB Vol.44(01) [January 2006]

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