Caloric restriction prevents age-related decline in skeletal muscle dihydropyridine receptor and ryanodine receptor expression.

The dihydropyridine receptor (DHPR), a voltage-gated L-type Ca2+ channel, and the Ca2+ release channel/ryanodine receptor isoform-1 (RyR1) are key molecules involved in skeletal muscle excitation-contraction coupling. We have reported age-related decreases in the level of DHPR expression in fast- and slow-twitch muscles from Fisher 344 cross Brown Norway (F344BNX) rats (Renganathan, Messi and Delbono, J. Membr. Biol. 157 (1997) 247-253). Based on these studies we postulate that excitation-contraction uncoupling is a basic mechanism for the decline in muscle force with aging (Delbono, Renganathan and Messi, Muscle Nerve Suppl. 5 (1997) S88-92). In the present study, we extended our studies to older ages and we intended to prevent or retard excitation-contraction uncoupling by restricting the caloric intake of the F344BNX rats from 16 weeks of age. Three age groups, 8-, 18-, and 33-month old caloric restricted rats, were compared with ad libitum fed animals. The number of DHPR and RyR1 and DHPR/RyR1 ratio (an index of the level of receptors uncoupling) in skeletal muscles of 8-month and 18-month rats was not significantly different in either ad libitum fed or caloric restricted rats. However, the age-related decrease in the number of DHPR, RyR1 and DHPR/RyR1 ratio observed in 33-month old ad libitum fed rats was absent in 33-month old caloric restricted rats. These results suggest that caloric restriction prevents age-related decreases in the number of DHPR, RyR1 and DHPR/RyR1 ratio observed in fast- and slow-twitch rat skeletal muscles.