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Although pregnancy is clearly associated with refractoriness to infused angiotensin II (AII) in the uteroplacental unit, there is still dispute over the mechanism by which angiotensin type 1 and type 2 receptors (AT 1 R and AT 2 R) may mediate this response in the uterine artery. This is in large part due to incomplete knowledge of levels of AT 1 R and AT 2 R expression and function in uterine artery endothelium (UA Endo) in the nonpregnant (NP) and pregnant (P) states, combined with the disagreement on whether AII may act through release of adrenomedullary catecholamines. The authors have previously described an increase in AT 1 R in UA Endo but not UA vascular smooth muscle (VSM) during pregnancy as compared to the nonpregnant intact ewe. Herein they report that the pregnancy-associated increase in AT 1 R expression in UA Endo is regulated by ovarian steroids. Using a recently developed antibody to AT 2 R, the authors now show there is no change in AT 2 R in UA Endo or VSM associated with ovarian function, and although AT 2 R is not changed in UA Endo by pregnancy, there is a significant decrease observed in UA VSM at that time. The authors also examined changes in receptors in UA Endo and VSM in estrogen (E2ß)-primed ewes in view of the common use of this model as a control for physiologic studies. In contrast to their findings in nonprimed nonpregnant or pregnant animals, the authors observed a significant increase in both AT 1 R and AT 2 R in UA Endo in response to the supraphysiologic priming with E2ß. In order to address the possible functionality of AT 1 R or AT 2 R in UA Endo, the authors used the uterine artery endothelial cell (UAEC) model of UA endothelial cells maintained in culture to passage 4. Differences in expression of AT 1 R or AT 2 R were normalized at passage 4 in P-UAECs and NP-UAECs. Treatment with AII activated phospholipase C (PLC) in both NP- and P-UAECs but signaling through the extracellular signal–regulated kinase (ERK) pathway was dramatically enhanced in P-UAECs compared to NP-UAECs. Surprisingly, both phosphoinositol turnover and ERK2 phosphorylation responses failed to display the expected dose-responses. Inhibition of AII-stimulated ERK2 phosphorylation with antagonists DUP 753 (AT 1 R, 10 µM) and PD 123319 (AT 2 R, 10 µM) failed to selectively inhibit ERK2 phosphorylation. The authors conclude that (a) the net effect of pregnancy may be an increase in the AT 1 R/AT 2 R ratio in both UA Endo and VSM but through apparently distinct mechanisms, (b) the ovariectomized animal model is similar to the luteal state for AT 1 R and AT 2 R expression, while the E2ß-primed model does not resemble the nonpregnant or pregnant state, and (c) there is a real possibility that AII may mediate its effects either through a complex AT 1 R-AT 2 R interaction or via an as-yet unidentified non-AT 1 , non-AT 2 receptor. [ABSTRACT FROM AUTHOR]

During gestation, placental blood flow, endothelial nitric oxide (NO) production, and endothelial cell nitric oxide synthase (eNOS) expression are elevated dramatically. Shear stress can induce flow-mediated vasodilation, endothelial NO production, and eNOS expression. Both the activity and expression of eNOS are closely regulated because it is the rate-limiting enzyme essential for NO synthesis. The authors adapted CELLMAX artificial capillary modules to study the effects of pulsatile flow/shear stress on ovine fetoplacental artery endothelial (OFPAE) cell NO production, eNOS expression, and eNOS phosphorylation. This model allows for the adaptation of endothelial cells to low physiological flow environments and thus prolonged shear stresses. The cells were grown to confluence at 3 dynes/cm 2 , then were exposed to 10, 15, or 25 dynes/cm 2 for up to 24 h and NO production, eNOS mRNA, and eNOS protein expression were elevated by shear stress in a graded fashion (p de novo ; i.e., inhibited by L-NMMA (N G -monomethyl-L-arginine) and reversed by excess NOS substrate L-arginine. Rises in NO production at 25 dynes/cm 2 (8-fold) exceeded (p [ABSTRACT FROM AUTHOR]

The marmoset adrenal is interesting as it is developmentally similar to humans and other primates, but in adulthood 17,20-lyase activity is very low. One possible explanation is an altered regulation of P450c17 expression by AT1-R. We investigated the expression and zonal distribution of the AT1-R in marmoset adrenal glands and adrenocortical cells in culture since it is known that AT1-R is a regulator of P450c17 expression and activity. AT1-R was expressed strongly in the ZG and to diminishing degrees through the remainder of the cortex. There was negative expression in a putative ZI. Dispersed adrenocortical cells retained AT1-R protein as detected by ICC. Cells cultured for several days and treated in serum-free media for 48 h maintained AT1-R expression, as measured by western. However, at that 48 h time point, treatment with Forsk, AII, TPA, or the combination of A + F or T + F did not appear to effect AT1-R expression. We conclude that marmoset adrenals express AT1-R similarly to humans and other higher mammals, adrenocortical cells retain AT1-R expression in culture, and consistent with other adrenal cell culture models, AT1-R expression is not lost in response to agonists long term. [ABSTRACT FROM AUTHOR]

Marmosets express a fetal zone during adrenal development but fail to produce significant amounts of C19 steroids in adulthood. It is not clear however if P450c17 regulation is different from that in humans/rhesus or the primary sequence is altered. To this end we isolated marmoset and rhesus adrenocortical cells, and treated the cells with known regulators of P450c17 expression for 48 h. P450c17 protein increased with Forskolin(F) treatment, but was marginally inhibited by AII(A) and TPA(T) alone. Combined A + F and T + F dramatically ablated the F response. Cortisol levels(EIA) increased upon F treatment and were inhibited by A and T. Combination of treatments partially inhibited the F-induced response. The protein-coding region of marmoset and rhesus P450c17 cDNAs were then isolated from adrenals using RT-PCR/TA cloning. Marmoset P450c17 shows one amino acid deletion but otherwise shares 90.6% and 91.4% homologies with the human and rhesus cDNA sequences, and 82.4% and 85% homologies with the human and rhesus predicted AA sequences, respectively. Since marmoset adrenocortical cells exhibit similar endocrine function to rhesus, impaired 17,20-lyase activity in the adult marmoset adrenal may in part be due to differences in the primary sequence. [ABSTRACT FROM AUTHOR]

Discusses topics and issues about receptors and signal transduction. Insights into the role of exercise in bypassing the morbid effects of MC4R knockout in mice models; Elucidation on the use of modern protein and cloning technology to address the issue of the function of the now cloned MC2R receptor; Discussion on issues of fatty acid metabolites in the control of steroidogenesis.