NAKAMURA, H., YAMAZAKI, M., CHIBA, Y., TAMURA, N., MOMOTSU, T., ITO, S., SHIBATA, A., KAMOI, K. and YAMAJI, T. Glomerular Filtration Response to Acute Loading with Protein from Different Sources in Healthy Volunteers and Diabetic Patients. Tohoku J. Exp. Med., 1990, 162 (3), 269-278- To evaluate the effects of acute protein loading on the glomerular filtration rate, albumin excretion rate and concentration of plasma amino acids, ten healthy volunteers and six type 2 diabetic patients with normoalbuminuria were studied before and after eating 0.7 g/kg body weight of tuna fish, boiled egg white, cheese or tofu (bean curd) on separate days. Furthermore, to study the possible role of glucagon, growth hormone, atrial natriuretic peptide and kallikrein in the responses of glomerular filtration rate to protein, these substances were measured before and after ingestion of tuna fish or egg white in six healthy volunteers. In healthy subjects, glomerular filtration rate increased significantly (p<0.01) from 98.1±4.2ml/min during the baseline period to 129.9±6.6ml/min after ingestion of tuna fish. No significant differences were seen between glomerular filtration rate before and after ingestion of egg white, cheese or bean curd. No significant differences were observed between the baseline albumin excretion rate and that after loading with any of the four kinds of protein. Plasma concentrations of alanine, glycine and arginine (amino acids known to induce glomerular hyperfiltration) increased to a greater degree after ingestion of tuna fish than after administration of the other meals. Diabetic subjects and healthy volunteers had similar responses. Plasma glucagon and growth hormone concentrations increased after ingestion of the tuna fish meal or egg white. Plasma atrial natriuretic peptide concentration and urinary kallikrein excretion were unaffected by ingestion of these two kinds of protein. These findings suggest that responses of glomerular filtration rate to acute protein loading may differ depending on the protein ingested, and that these reponses may not be directly induced by glucagon, growth hormone, atrial natriuretic peptide or kallikrein.