Effect of colchicine on the uptake of prolactin and insulin into Golgi fractions of rat liver.

Abstract

In previous studies we have shown that 125I-labeled prolactin is taken up by a receptor-dependent process and concentrated in an intact form in Golgi elements from female rat liver (J. Biol. Chem., 1979, 254:209-214). In this study we have examined the effect of colchicine on this uptake process into Golgi elements. Colchicine [25 mumol (10 mg)/100 gm body wt] was injected intraperitoneally in adult female rats, and hepatic Golgi fractions were prepared at 1, 2, and 3 h postinjection. The enzyme recoveries and morphological appearance of fractions from colchicine-treated and control (alcohol alone) animals were similar. At times greater than 1 h after colchicine there was a marked (greater than 60%) inhibition of uptake of 125I-ovine prolactin (125I-oPRL) into Golgi light and intermediate fractions but no inhibition of uptake into Golgi heavy and plasmalemma elements. At times from 2 to 45 min postinjection, 125I-oPRL was extracted from Golgi elements and found to be largely intact as judged by rebinding to receptors. The inhibitory effect of colchicine was seen at doses ranging from 0.25 mumol to 25 mumol/100 g body wt. Vincristine also inhibited 125I-oPRL uptake into the Golgi light and intermediate fractions but lumicolchicine had no inhibitory effect. There was a smaller effect of colchicine both at early (1 h) and later (3 h) times on the extent and pattern of 125I-insulin uptake. Colchicine treatment did not produce a significant change in lactogen receptor levels in the Golgi fractions. These results demonstrate that colchicine treatment inhibited the transfer of prolactin into Golgi vesicular elements. The much smaller effect on insulin uptake suggests that there may be differences in the manner in which the two hormones are handled in the course of internalization.

Effect of colchicine on internalization of prolactin in female rat liver: an in vivo radioautographic study.

“…At later intervals a greater proportion of grains was observed over the larger structures in this compartment. The small vesicles observed in the present study corresponded in size and temporal labeling to the small smooth-surfaced vesicles which accounted for the labeling of the Golgi heavy fraction in previous studies assessing 12SI-oPRL internalization by subcellular fractionation (17,26). Our combined in vivo studies of the present work and previous subcellular fractionation data (17,26) therefore indicate a sequence of internalization involving initial binding of hormone to the sinusoidal and lateral surfaces of the plasmalemma followed by internalization into small, smooth-surfaced intracytoplasmic vesicles and temporary accumulation within vesicles with a lipoprotein content.…”

“…As galactosyl transferase rela-3 The demonstration of internalized LDL into lipoprotein containing vesicles (11) raises the possiblity that some of the content of such vesicles both in our Golgi apparatus fractions as well as in situ represents internalized as opposed to secretory lipoproteins. tive specific activities and recoveries were identical for Golgi fractions isolated from control or colchicine-treated rats (26), then the labeled lipoprotein-containing structures observed in the present work ( Fig. 10) may represent a subpopulation of lipoprotein-containing vesicles which do not accumulate in microsomes and are not enriched in galactosyl transferase marker enzyme.…”

Exocytotic exposure and retrieval of membrane antigens of chromaffin granules: quantitative evaluation of immunofluorescence on the surface of chromaffin cells.

“…The profiles obtained with these drugs are therefore not shown in the figure . endocytotic uptake have been published. Colchicine, interfering with microtubules, has been shown to reduce endocytotic uptake of lysosomal enzymes (28) and to inhibit receptormediated uptake of prolactin and transfer into the Golgi region (19). In the latter case, colchicine may have interfered less with uptake than with the subsequent transfer step.…”

Uptake of Insulin and Other Ligands into Receptor-Rich Endocytic Components of Target Cells: The Endosomal Apparatus

“…Indeed, the term lysosomotropic agent has been recently renamed acidotropic agent (39a). Microtubule polymeriza tion is also directed at endosomal structures, as are temperatures less than 20°C (18,48,73,110,125,167). The temperature effects may indicate a unique lipid composition of the phospholipid bilayer of "late" endosomes that must undergo an alteration of the membrane bilayer structure in order to enable membrane coalescence, presumably with secondary or primary lysosomes.…”