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The effect of continuous and repetitive mechanical stretch on release of immunoreactive atrial natriuretic factor (IR-ANF) was studied in isolated rat atria distended by inflation of miniature balloon catheters. After 10 min incubation, the concentration of IR-ANF in the medium increased in proportion to the degree of continuous atrial stretch. Repetitive atrial expansion induced a rate dependent increase in release of IR-ANF which at the highest rate tested (89 inflations/min) was sixfold greater than that observed with continuous maximal expansion. Comparison of the amount of IR-ANF released from the right or left atrium separately revealed that during continuous and repetitive stretch, both atria contribute equally to the total amount of release IR-ANF. A reduction of bath temperature (37 degrees to 21.5 degrees C) decreased both basal- and stretch-induced IR-ANF release approximately 85%. It was concluded that release of atrial natriuretic factor is temperature-dependent and induced by both the extent and rate of atrial stretch.
Bilder et al. (Sat,) studied this question.