Glutamic acid potentiates hepatocyte response to mitogens in primary culture.
Adult rat hepatocytes in primary culture responded to epidermal growth factor (EGF) by increased DNA synthesis. When hepatocytes were cultured in Leibovitz L-15 medium, their response to EGF was low compared with that in Williams' medium E or Koga's medium L. Furthermore, female rat hepatocytes showed almost no response to the mitogenic action of EGF compared with male rat hepatocytes in L-15 medium. Addition of glutamic acid (1-20 mM) to EGF-containing L-15 medium not only enhanced DNA synthesis > tenfold in both male and female hepatocytes, but eliminated the sex differences in DNA synthesis. Aspartic acid, glutamine, or ornithine at 20 mM did not replace the glutamic acid effect on DNA synthesis. Proline also enhanced EGF-induced DNA synthesis, although it was less effective than glutamic acid. Therefore, this effect may be specific to a high concentration of glutamic acid. Glutamic acid by itself did not stimulate DNA synthesis at any concentrations tested. In the presence of glutamic acid, EGF showed a dose-dependent (0.5-20 ng/ml) stimulation of DNA synthesis with a maximal effect at 10 ng/ml. Almost the same effect was obtained with transforming growth factor alpha (0.5-20 ng/ml). Glutamic acid also induced an expansion of the mitogenic action of angiotensin II. Since glutamic acid did not affect [125I]EGF binding to hepatocytes or its processing, the effect may occur internal to the receptor. These results suggest that glutamic acid modulates the sensitivity of the hepatocyte response to mitogens.
Hasegawa
K
K
Department of Surgery, University of Pittsburgh School of Medicine, Pennsylvania 15213.
Miyata
Y
Y
Carr
B I
BI
D000596:Amino Acids / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D003470:Culture Media / Q000494:pharmacology; D004247:DNA / Q000096:biosynthesis; D004815:Epidermal Growth Factor / Q000378:metabolism; D005260:Female; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D006133:Growth Substances / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008934:Mitogens / Q000494:pharmacology*; D011392:Proline / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D012727:Sex Characteristics
D000596:Amino Acids; D003470:Culture Media; D005971:Glutamates; D006133:Growth Substances; D008934:Mitogens; D000804:Angiotensin II; D018698:Glutamic Acid; D004815:Epidermal Growth Factor; D004247:DNA; D011392:Proline