epidermal-growth-factor and estrone-sulfate

It was shown previously that OAT3 activity was differentially regulated by protein kinases including MAPK, PKA, and PKC. The present study investigated the short-term effect of tyrosine kinase and phosphatidylinositol 3-kinase (PI3K) on OAT3-mediated organic anion transport in S2 segments of renal proximal tubules. Genistein, a tyrosine kinase inhibitor, and wortmannin, a PI3K inhibitor, inhibited transport of estrone sulfate, a prototypic substrate for OAT3, in a dose-dependent manner. Previously, we showed that epidermal growth factor (EGF) stimulated OAT3 activity via the MAPK pathway. In the present study, we investigated whether EGF-stimulated OAT3 activity was dependent on tyrosine kinase and PI3K. We showed that EGF stimulation of OAT3 was reduced by inhibition of tyrosine kinase or PI3K, suggesting that they play a role in the stimulatory process. Inhibitory effects also indicated that tyrosine kinase and PI3K are involved in the MAPK pathway for EGF stimulation of OAT3 in intact renal proximal tubules, with PI3K acting upstream and tyrosine kinase acting downstream of mitogen-activated/extracellular signal-regulated kinase kinase activation.

Topics: Androstadienes; Animals; Enzyme Inhibitors; Epidermal Growth Factor; Estrone; Genistein; Ion Transport; Kidney Tubules, Proximal; Organic Anion Transporters, Sodium-Independent; Phosphatidylinositol 3-Kinases; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Rabbits; Wortmannin

The formation of oestrone sulphate has been examined in MCF-7 (oestrogen receptor positive, ER+) and MDA-MB-231 (ER negative, ER-) breast cancer cells. Using intact cell monolayers and a physiological substrate concentration, progesterone (1 microM) and dexamethasone (1 microM) both increased oestrone sulphate formation in MCF-7 cells. In MDA-MB-231 cells, dexamethasone, but not progesterone, increased conjugate formation. A number of growth factors, cytokines and human serum albumin (HSA), which have previously been found to regulate oestrogen synthesis, were also examined for their ability to regulate oestrone sulphate formation. In MCF-7 cells epidermal growth factor, acidic and basic fibroblast growth factors, insulin-like growth factor-type I and insulin all stimulated oestrone sulphate formation. The cytokines, tumour necrosis factor alpha (TNFalpha) and interleukin-1beta also increased conjugate formation in the ER+ cells, as did HSA. In contrast, in MDA-MB-231 cells TNFalpha was without effect and HSA inhibited oestrone sulphate formation. The ability to modulate oestrone sulphate formation in ER+ cells may be an important mechanism to limit the availability of oestrogen to interact with the ER.

Topics: Breast Neoplasms; Cytokines; Epidermal Growth Factor; Estrone; Female; Fibroblast Growth Factor 1; Fibroblast Growth Factor 2; Growth Substances; Humans; Insulin; Insulin-Like Growth Factor I; Insulin-Like Growth Factor II; Interleukin-1; Interleukin-2; Interleukin-6; Kinetics; Receptors, Estrogen; Serum Albumin; Time Factors; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha

In this paper we examine the ability of the mammary gland to remove from circulating blood three compounds which differ in their physico-chemical and structural properties. Mammary extraction of progesterone, oestrone sulphate and epidermal growth factor (EGF) is similar at peak lactation in goats, but the proportion of labelled infusate that is transferred into milk is greater for oestrone sulphate and EGF than progesterone which is rapidly metabolised by mammary tissue. The kinetics of transfer of progesterone, oestrone sulphate and EGF from blood into milk show that transcellular processes are involved, and on the basis of earlier hypotheses and new information reported here the results indicate the probable importance of simple and facilitated diffusion pathways for progesterone and oestrone sulphate, and secretory mechanisms for oestrone sulphate and EGF. Although evidence is lacking for a direct effect of hormones in milk on mammary function, their concentration in milk may reflect changes in local regulation of mammary secretion. Considerable practical value is attached to the immunodiagnostic use of milk hormone concentrations to determine ovarian and placental endocrine activity during pregnancy in domestic ruminants.

Topics: Animals; Biological Transport; Cattle; Epidermal Growth Factor; Estrone; Female; Goats; Growth Substances; Kinetics; Lactation; Mammary Glands, Animal; Milk; Pregnancy; Pregnancy Tests; Progesterone; Prostaglandins F; Steroids

The purpose of the present investigation was to characterize and determine what hormones affect the activity of aromatase in human fetal hepatocytes maintained in primary monolayer culture. The major product of aromatization of androstenedione was estrone sulfate. Optimal conditions for assay of aromatase activity in fetal liver cells were determined. The apparent Km for androstenedione was 50 nM. Aromatase activity was stimulated by glucocorticoids in the presence of fetal calf serum. The concentration of dexamethasone required for half-maximal stimulation was 10(-8) M, similar to the concentration required for half-maximal binding to glucocorticoid receptors. This action of dexamethasone was inhibited by cortisol 21-mesylate, a glucocorticoid antagonist. Aromatase activity was also stimulated by (Bu)2cAMP and cholera toxin, and was inhibited by fetal calf serum. This effect of fetal calf serum was mimicked by epidermal growth factor. However, epidermal growth factor did not mimic the permissive action of serum to stimulate aromatase activity by dexamethasone. In these respects, the regulation of aromatase activity of human fetal hepatocytes is similar to that of human adipose stromal cells. A polycyclic hydrocarbon, benzo(a)pyrene, which causes induction of aryl hydrocarbon hydroxylase activity in fetal hepatocytes, inhibited the stimulation of aromatase activity by dexamethasone. Of a number of hormones tested, including glucagon, insulin, angiotensin II, ACTH, hCG, GH, PRL, and T3, only glucocorticoids were effective in stimulating aromatase activity of human fetal hepatocytes. These results emphasize the complex and multiparameter nature of the regulation of aromatase activity in this as in other tissues.

Topics: Androstenedione; Aromatase; Bucladesine; Cells, Cultured; Dexamethasone; Epidermal Growth Factor; Estrogens; Estrone; Fetal Blood; Humans; Hydrocortisone; Kinetics; Liver; Microsomes, Liver; Oxidoreductases