Isoprenaline reverses the slow force responses to a length change in isolated rabbit papillary muscle
✍ Scribed by Jonathan C. Kentish; Richard Davey; Penny Largen
- Publisher
- Springer
- Year
- 1992
- Tongue
- English
- Weight
- 323 KB
- Volume
- 421
- Category
- Article
- ISSN
- 0031-6768
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✦ Synopsis
An alteration in the length of isolated cardiac muscle produces an immediate change in twitch force, then a slow further change in the same direction. We have found that the slow changes in force in rabbit papillary muscles are blocked or reversed by the l~agonist, isoprenaline (1 t,M). The abolition of the slow responses by isoprenaline was not due to saturation of the myofibrils with Ca 2 § as the blockade continued if the extracellular [Ca 2 § was reduced in the presence of isoprenaline so that twitch force was <50% maximal. Ryanodine (1 aM) did not block the slow responses, suggesting that the sarcoplasmic reticulum does not mediate the responses. These results suggest that changes of intracellular [cAMP] may mediate, or at least modulate, the slow force responses to a length change in cardiac muscle.