Effects of gadolinium on length-dependent force in guinea-pig papillary muscle.
The degree to which stretch-activated channels operate during physiological length changes in multicellular heart preparations, or how much the channels could contribute to length-dependent activation, is not known. We studied the relationship between muscle length and contractile force in guinea-pig papillary muscles superfused with gadolinium chloride (10 microM), a stretch-activated channel blocker, and compared the effects to those with nifedipine (0.25 microM), a calcium channel blocker. Gadolinium reduced contractile force statistically significantly more at the longer muscle lengths than at the short muscle lengths. This did not apply with nifedipine, although a marginally greater effect at longer lengths was perceptible. The results can only partly be explained by gadolinium having a non-specific action via the calcium channel, or Na(+)-Ca2+ exchange, and are consistent with the possibility that stretch-activated channels contribute to length-dependent activation in cardiac muscle, and thus to 'Starling's Law of the Heart'.
Lab
M J
MJ
Department of Physiology, Charing Cross and Westminster Medical School, London.
Zhou
B Y
BY
Spencer
C I
CI
Horner
S M
SM
Seed
W A
WA
D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D005682:Gadolinium / Q000494:pharmacology*; D006168:Guinea Pigs; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology; D010210:Papillary Muscles / Q000187:drug effects* / Q000502:physiology*
D005682:Gadolinium; D009543:Nifedipine