Endocytosis of simple proteins by rat yolk sacs and by rat peritoneal macrophages incubated in vitro.
The specificity of endocytosis of the 125I-labelled forms of LDH H4 and M4 and BSA was investigated in rat yolk sac and resident rat peritoneal macrophages incubated in vitro. The rate of uptake of the more basic LDH M4 by yolk sac is only slightly higher than that of LDH H4, but in macrophages the isoenzyme M4 is taken up three times more rapidly than the H4 form. Both cell types possess little affinity for BSA, but an increase in the hydrophobicity of this protein by formaldehyde-denaturation resulted in a several-fold increase in uptake by yolk sac cells as well as by macrophages. Apparently, yolk sacs and macrophages both contain binding sites for positively charged and hydrophobic proteins, but, in yolk sac hydrophobicity is relatively more important, whereas in macrophages positive charge is the main characteristic for adsorptive pinocytosis of simple proteins. In this respect, the binding characteristics of peritoneal macrophages resemble those of sinusoidal liver cells. The study also compares the serum-dependence of fluid-phase pinocytosis in both cell types; a decrease in serum concentration gives rise to an increase in the rate of pinosome formation in yolk sac, but has the opposite effect in macrophages.
D000818:Animals; D001769:Blood; D004705:Endocytosis; D007527:Isoenzymes / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D010873:Pinocytosis; D011205:Povidone; D011489:Protein Denaturation; D051381:Rats; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D015017:Yolk Sac / Q000378:metabolism*
D007527:Isoenzymes; D012710:Serum Albumin, Bovine; D007770:L-Lactate Dehydrogenase; D011205:Povidone