Archive for the 'Pregnant Rats' Category

14 Jun

Modulation of Calcium Mobilization: DISCUSSION(9)

It is considered that a hyperpolarization of 2 mV could decrease the probability of there being open channels by around 30%, meaning that a greater proportion of the channels are in a closed state—theconformationofthe channels to which blockers have the lower affinity. It should be noted that Meyer et al. have shown that smooth muscle […]

13 Jun

Modulation of Calcium Mobilization: DISCUSSION(8)

We have previously shown that the decreased effect of Bay K 8644 on aortic rings of pregnant rats can be modulated with KCl. In the present study, we have observed a reduced Bay K 8644-stimulated 45Ca2+ uptake on aortic rings from pregnant rats. Calcium channel modulators act by changing the opening probability of channels—activators (Bay […]

12 Jun

Modulation of Calcium Mobilization: DISCUSSION(7)

Indeed, 45Ca2+ uptake was stimulated by a dihydropyridine calcium channel activator, Bay K 8644. Both basal and Bay K 8644-stimulated 45Ca2+ uptake were significantly higher in aorta of virgin than of pregnant animals. We have previously reported that the contractile effect of Bay K 8644 is markedly reduced during pregnancy; the present results suggest that […]

11 Jun

Modulation of Calcium Mobilization: DISCUSSION(6)

Specific binding of [3H]isradipine was examined over a wide range of KCl concentrations in the intact aorta from spontaneously hypertensive and Wistar-Kyoto rats. These results indicated that proportions of 30% and 5% of calcium channels were in a high-affinity state in aorta of Wistar-Kyoto and spontaneously hypertensive rats, respectively, under physiological conditions. We have performed […]

10 Jun

Modulation of Calcium Mobilization: DISCUSSION(5)

Calcium influx is needed for the tonic component of vascular smooth muscle contraction. It was reported that when the concentration of CaCl2 in the bathing solution was reduced to 0.8 from 1.6 mM, responses of aortic rings of pregnant rats to phenylephrine were less affected than those of their nonpregnant counterparts. These authors conclude that […]

09 Jun

Modulation of Calcium Mobilization: DISCUSSION(4)

Calcium channel blockers bind to the voltage-operated calcium channels and block voltage-dependent calcium influx. In so doing, they interfere with induced contractions. The efficacy of D-600 was lower on tissues of pregnant rats under both phenylephrine and KCl (Fig. 3). The concentration-response curves to KCl in the presence of D-600 were similar to the ones […]

08 Jun

Modulation of Calcium Mobilization: DISCUSSION(3)

We have previously reported that extracellular calcium mobilization could be impaired during pregnancy. To evaluate the influence of extracellular calcium in the decreased vascular reactivity of gestation, we measured con-centration-response curves to CaCl2 on aortic rings prestimulated, in the absence of CaCl2, by receptor-dependent (phenylephrine) and voltage-dependent (KCl) stimuli (Fig. 2). Our results did not […]

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