ATRIAL-NATRIURETIC-PEPTIDE IN PLASMA AFTER PROLONGED PHYSICAL STRAIN,ENERGY DEFICIENCY AND SLEEP-DEPRIVATION

Plasma concentrations of atrial natriuretic peptide (ANP) were investi gated daily in 16 male cadets during a 6-day military training course with continuous heavy physical activities, sleep and energy deficiency (course I). At the end of another similar course (course II) 15 cadet s were studied during 30-min cycle exercise at 50% maximal oxygen upta ke with and with out glucose infusion. A small, but not significant in crease was found in the plasma concentrations of ANP during course I f rom 9.6 (SEM 1.1) pmol.l(-1) in the control experiment to 11.1 (SEM 0. 5) pmol.l(-1) on day 5. During course II a small but significant incre ase was found from 7.8 (SEM 0.5) pmol.l(-1) in the control experiment to 9.1 (SEM 0.5) pmol.l(-1) at the end of the course. Plasma osmolalit y and chloride concentration decreased during the course. During the e xercise test a significant increase was seen in ANP concentration from 8.2 (SEM 0.8) to 13.1 (SEM 2.0) pmol.l(-1) in the control experiment and from 9.4 (SEM 0.7) to 13.5 (SEM 1.2) pmol.l(-1) during the course. This response was attenuated by glucose infusion, an effect which may have been due to an exercise induced increase in plasma chloride conc entration being abolished. In contrast, the potassium concentration re sponse to exercise was increased during the course but unaffected by g lucose infusion. In conclusion, the large increases in endogenous plas ma catecholamine concentration shown to take place during previous cou rses were not reflected in the plasma concentrations of ANP, indicatin g only a moderate cardiac stress or no cardiac work overload during su ch courses.