EFFECTS OF TEMPERATURE ON MUSCLE PHI AND PHOSPHATE METABOLITES IN NEWTS AND LUNGLESS SALAMANDERS

The effect of acute alterations in body temperature (BT) on intracellu lar pH (pH(i)) and phosphate metabolites was assessed in white skeleta l muscle of intact newts and lungless red-backed salamanders using P-3 1-nuclear magnetic resonance spectroscopy. pH(i) decreased with increa sing BT in the tail muscle of both newts and lungless red-backed salam anders. The change in pH with change in temperature from 10 to 30-degr ees-C was -0.018 U/degrees-C in newts and -0.041 U/degrees-C in red ba cks. The calculated alpha-imidazole for skeletal muscle cytosol did no t change (0.56) in newts from 10 to 30-degrees-C but fell from 0.69 to 0.43 in red-backed salamanders. Phosphocreatine (PCr)/P(i) fell and P (i)/beta-ATP rose with increasing temperature in both newts and red ba cks; however, the change was much greater in red backs. Providing the red backs with O2 at 30-degrees-C led to higher pH and alpha-imidazole , comparable to that of newts, along with increased PCr/P(i) and lower P(i)/beta-ATP. Thus newts maintain white skeletal muscle cell cytosol alpha-imidazole constant with changes in BT, whereas red backs appare ntly do not. However, at the BT of preference, red backs and newts mai ntain similar muscle pH(i) and alpha-imidazole. The method of gas exch ange appears to strongly influence the ability of an animal to maintai n its acid-base status over a range of temperatures, and our results s uggest that behavioral regulation of BT may involve alpha-imidazole re gulation as well.