Key result
Isoprenaline triggers exaggerated positive inotropism and lacks relaxing effects in young cardiomyopathic hamster papillary muscles.
Why the study?
Does isoprenaline alter the mechanophysiological response of papillary muscles from young cardiomyopathic hamsters compared to normal hamsters?
Does isoprenaline alter the mechanophysiological response of papillary muscles from young cardiomyopathic hamsters compared to normal hamsters?
Young cardiomyopathic hamster papillary muscles show an exaggerated inotropic response and absent relaxing effect to isoprenaline, suggesting inadequate calcium regulation under sympathetic stimulation.
Answers are grounded in this paper and cite their sources.
Does not inform isoprenaline use in patients; hypothesis-generating for early calcium dysregulation in genetic cardiomyopathy.
Papillary muscles isolated from the left ventricle of 17-20 day old Syrian hamsters with genetic cardiomyopathy (BIO 14.6 strain) were examined for their mechanophysiological response to the beta adrenoceptor agonist isoprenaline. The indices of isometric twitch for both myopathic and aged matched normal (BIO RB strain) hamster papillary muscles were statistically the same before exposure to catecholamine. Isoprenaline, however, elicited an exaggerated degree of positive inotropism in myopathic papillary muscles. In addition, the characteristic relaxing effect of beta adrenoceptor agonists (abbreviation of twitch duration) was virtually absent in myopathic muscles. These results suggest that under conditions resembling sympathetic stimulation sarcolemma and perhaps sarcoplasmic reticulum become inadequate regulators of calcium, predisposing young myopathic heart cells to accrue damaging concentrations of sarcoplasmic calcium.
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Rossner et al. (1986) studied Genetic cardiomyopathy. Isoprenaline vs. Age-matched normal hamster papillary muscles was evaluated on Mechanophysiological response (indices of isometric twitch). Isoprenaline elicited an exaggerated degree of positive inotropism and lacked the characteristic relaxing effect in papillary muscles from young cardiomyopathic hamsters compared to normal controls.
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