Transport of amino acids into the oestrogen-primed uterus. Enhancement of the uptake by a preliminary incubation

Abstract

1. Preincubation of the immature rat uterus under physiological conditions was found to increase its subsequent ability to transport alpha-aminoisobutyric acid, l-proline, l-alanine and 1-aminocyclopentanecarboxylic acid. Uptakes of l-valine, l-phenylalanine and l-leucine were not affected. With alpha-aminoisobutyric acid, a doubling of the uptake could be obtained after a 3-5h preincubation period. Uteri from oestradiol-primed rats gave increases similar to those found in tissues from untreated animals. In both cases the preincubation increased the V(max.) of alpha-aminoisobutyric acid uptake but did not affect the K(m). 2. The conditions during the preincubation period determined the increase in subsequent uptake of alpha-aminoisobutyric acid. No increase in uptake was found if the preincubation was carried out at 1 degrees C, in the presence of cyanide or dinitrophenol, under anaerobiosis or with a concentration of puromycin that depressed incorporation of l-leucine into protein by 95%. The puromycin was also shown to prevent the increase in V(max.) normally found after the preincubation period. In addition, no increase was found if Na(+) was omitted from the preincubation medium. Other inorganic ions had smaller effects. 3. The uptake of alpha-aminoisobutyric acid by uteri before and after a preincubation period showed the same general patterns of sensitivity to competitive inhibitors, K(+), pH, temperature and 2,4-dinitrophenol. 4. The results suggest that the preincubation leads to an increase in a protein component of the ;A system' for amino acid transport in the uterus, and that metabolic energy is required for the reactions involved.

Placental Amino Acid Uptake. II. Tissue Preincubation, Fluid Distribution, and Mechanisms of Regulation

“…Studies with inhibitors now indicate that this process requires protein synthesis and aerobic metabolism. In these respects it is apparently similar t o increases in amino acid transport described in immature chick and rat muscle tissue (8-10) and rat uterus (20) and found t o be limited to a particular transport system. This mechanism appears t o involve synthesis of a protein which is rate limiting t o transport, perhaps a component of a membrane carrier system.…”

Amino acid transport in isolated rat hepatocytes

“…This phenomenon was originally described by Gazzola,Franchi,Saibene,Ronchi and Guidotti (i[972) in chick embryo heart cells and, independently, that same year by Riggs and Pan (1972) for rat uterus.…”

Induction of stress proteins in chicken embryo cells by low‐level zinc contamination in amino acid‐free media

“…The activity of one of the major neutral amino acid transport systems (A system) increases dramatically following incubation of animal cells in amino acidfree medium (Gazzola et al, 1972;Riggs and Pan, 1972) and regulation appears to be at the transcriptional level (Gazzola et al, 1981).…”