Effect of cold stress on the subcellular distribution of noradrenaline in the rat heart

Abstract

Rats were exposed to cold (4") for 2 hr to study the effect of increased sympathetic activities on the subcellular distribution of noradrenaline in the heart. Coldexposure caused about 30% decrease of total noradrena!ine contents in both auricles and ventricles of normal or adrenalectomized rats. This depletion of noradrenaline caused by cold was completely prevented by pretreatment of the rat with hexamethonium chloride. Measurement of the subcellular distribution of noradrenaline revealed that the percentage depletion in particle-bound amine in both auricles and ventricles was greater than in the supernatant noradrenaline. It is suggested that the noradrenaline in the particulate fraction is the functional pool of the amine available for release by nerve impulses. Methods COLD STRESSLong Evans rats of either sex, 250 to 300 g, were placed in a cold room at 4" for 2 hr after which the rats were killed by a blow on the head. The heart was then rapidly excised.

Studies on the Interactions of Guanethidine and Bretylium With Noradrenaline Stores

“…This evidence would make the conclusion made by Cass & Spriggs (1961), Gaffney et al (1963) and Spriggs (1966) based on assay of the total tissue noradrenaline untenable. Since the transmitter amine available for release on-sympathetic nerve stimulation has been shown to reside in the particulate fraction of the vas deferens (Chang & Chang, 1965) as well as of the heart (Hift & Campos, 1962 ;Chang & Su, 1967) it is tempting to suggest that the adrenergic neurone-blocking effect of guanethidine may be due to a rapid depletion of the functional amine pool in the particulate fraction. This effect could be a displacement, since guanethidine is also retained by the particulate fraction, or could be due to an inhibition of the intracellular amine-concentrating mechanism (Shore & Giachetti, 1966).…”