DECREASED PROTEIN-SYNTHESIS DURING DRY SATURATION DIVING

Changes in metabolism during saturation dives have been reported; howe ver, these changes have not been well defined. This study was conducte d to determine the effect of saturation diving on protein metabolism. Whole body protein synthesis was measured by the ammonia and urea endp oint methods, following a single oral dose of N-15-glycine in 11 Navy divers 33.9 +/- 1.9 yr of age. The divers were fed a controlled diet t hroughout the three trials. Trial I was on the surface, and trials II and III were during dry saturation dives at 0.56 MPa. The protein synt hesis results in gram protein per kilogram lean body mass per day, lea st square mean +/- SD: Trial I Trial II Trial III Ammonia 4.31 +/- 0.3 4 2.48 +/- 0.34 2.00 +/- 0.34 Urea 4.26 +/- 0.33 3.70 +/- 0.33 2.80 +/ - 0.33 Under the conditions of this series of dry saturation dives, pr otein synthesis was depressed by up to 30-50% for the urea and ammonia endpoint methods, respectively. An estimate of liver protein synthesi s was made by measuring the incorporation of the N-15 label into plasm a fibrinogen. The N-15 enrichment of fibrinogen glycine and the hippur ate precursor for fibrinogen were decreased significantly. This dramat ic decrease in protein synthesis was observed despite positive nitroge n balance in these divers. Although further investigation is needed to elucidate the mechanism, the decrease in the incorporation of N-15 gl ycine into fibrinogen suggests alteration in liver nitrogen metabolism at 0.56 MPa.