Control of angiotensinogen production by H4 rat hepatoma cells in serum-free culture

Elevated des-AngI-angiotensinogen levels by nephrectomy and adrenalectomy

This study investigates the time course of plasma levels of angiotensinogen (Aogen) and of the Aogen metabolite des-AngI-angiotensiongen (des-AngI-Aogen) in nephrectomized rats with and without adrenals for 24 h. After nephrectomy the plasma Aogen levels increased 5-fold over the following 24 h. The increase is significantly lower after sham nephrectomy (3.7-fold, P < 0.05) and if the kidneys are withdrawn without decapsulization (2.4-fold, P < 0.05). A small and transient increase arise after nephrectomy plus adrenalectomy (1.6-fold after 8 h, P < 0.005). After adrenalectomy alone Aogen levels continuously shrink to 38% of control values after 24 h. Plasma des-AngI-Aogen levels increase 2.1- to 3.7-fold 24 h after the different nephrectomy procedures. In connection with recent findings these data support the notion that the increase in Aogen plasma levels after bilateral nephrectomy is triggered by renin, released during surgery. High plasma levels of des-AngI-Aogen after nephrectomy indicate that AngI is generated by tissue renin, e.g., in the adrenals. This suggests that after nephrectomy the plasma des-AngI-Aogen levels should be a valuable proof for the evaluation of the amount of generated angiotensin.

A novel inhibitory role for glucocorticoids in the secretion of angiotensinogen by C6 glioma cells

Astrocytes have been identified as the primary source of brain angiotensinogen (Ao), but the regulation of the secretion of this protein from astrocytes is poorly defined. In this study, the rat C6 glioma cell line was used as an astrocyte model to investigate the regulation of Ao secretion. C6 cultures secreted Ao at a rate of 4.05 +/- 1.52 (mean +/- SD) ng of Ao/10(6) cells/24 h as determined by a direct radioimmunoassay. This rate was not significantly altered by the hormones thyroxine, estradiol, angiotensin II, growth hormone, and prostaglandins or by increased levels of intracellular cyclic AMP. Treatment with the synthetic glucocorticoid dexamethasone (DEX; 10(-6) M) reduced the rate of Ao secretion to 1.82 +/- 0.28 ng of Ao/10(6) cells/24 h. By comparison, the basal secretion rate for rat H4 hepatoma cells was 142.4 +/- 10.0 ng of Ao/10(6) cells/24 h, and this increased fourfold (572.4 +/- 173.1 ng/10(6) cells/24 h) in the presence of 10(-6) M DEX. Both these inhibitory (C6) and stimulatory (H4) actions of DEX were dose related. The inhibition observed in C6 cells was mimicked by RU28362, a pure glucocorticoid agonist, and reversed by the antagonist RU486, demonstrating that DEX was functioning as a true glucocorticoid. The action of DEX was also antagonized by the cyclic AMP analogue N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (dBcAMP) (control, DEX, and DEX + dBcAMP, 3.58 +/- 0.73, 1.69 +/- 0.82, and 4.93 +/- 1.88 ng of Ao/10(6) cells/24 h, respectively, and by the beta-adrenergic agonist isoprenaline, which stimulates cyclic AMP production.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II is the mediator of the increase in hepatic angiotensinogen synthesis after bilateral nephrectomy

The present study investigated the hypothesis that the increase in plasma angiotensinogen after nephrectomy is mediated by endogenous renin and angiotensin (ANG) II. Rats were divided into control, nephrectomy, or nephrectomy plus adrenalectomy groups. In addition, similar cohorts were divided as just mentioned and then given either atenolol (selective beta 1-adrenoceptor inhibitor that prevents renin release) or Dup-753 [ANG II (AT1) receptor antagonist]. The plasma angiotensinogen levels increase approximately fivefold after 24 h in nephrectomized rats. Pretreatment with atenolol blunted this increase. A significant reduction was observed 4 h (P < 0.05) and 8 h (P < 0.005) after surgery. Dup-753 nearly abolished the increase in angiotensinogen plasma levels. After pretreatment with Dup-753, significantly higher angiotensinogen levels (P < 0.005) were found only after 24 h. Nephrectomy plus adrenalectomy also blunted the rise in plasma angiotensinogen. A significant increase in angiotensinogen plasma levels could only be observed after 8 h (P < 0.005) and 12 h (P < 0.005) but not after 24 h. Atenolol further reduced this increase. After atenolol pretreatment, significantly higher angiotensinogen levels could only be observed after 12 h (P < 0.05). Dup-753 completely abolished the increase of plasma angiotensinogen after nephrectomy plus adrenalectomy. In anesthetized control rats at time 0 the plasma ANG I levels were 0.7 nM. Pretreatment with atenolol decreased the ANG I values by 30%, whereas Dup-753 caused a sixfold increase in plasma ANG I levels in the control rats at time 0.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the renin-angiotensin system after nephrectomy and adrenalectomy

The study investigates the change in angiotensinogen (Aogen), angiotensin I (AngI) and renin plasma concentration after nephrectomy and adrenalectomy. The aim of the study was to elucidate the mechanisms that are involved in the up regulation of the Aogen plasma levels after nephrectomy and the contribution of the adrenals. Rats were treated with the beta 1-selective adrenoceptor blocker, atenolol, and with the angiotensin antagonist, DuP 753 in order to inhibit renal renin release and to check whether the increase in plasma Aogen after nephrectomy is mediated by angiotensin (AngII), respectively. The plasma Aogen levels increase approx. 5-fold 24 h after nephrectomy. This increase is significantly reduced in the presence of atenolol. After nephrectomy plus adrenalectomy there is a maximal increase of 60% in plasma Aogen levels 8 h after surgery and a subsequent decline. In the presence of atenolol this increase is even smaller. In contrast after adrenalectomy the plasma Aogen levels continuously declined. In the presence of atenolol the plasma Aogen levels were approx. 20% higher at time 0 but declined with the same slope as after adrenalectomy without atenolol treatment. Treatment with DuP 753 caused an almost complete inhibition of the increase in Aogen plasma levels after nephrectomy. Significantly higher Aogen levels were found only after 24 h. At time 0, immediately after nephrectomy the plasma AngI levels were increased compared to the respective control rats. Significantly higher AngI values (P < 0.05) could also be observed in nephrectomized rats and in nephrectomized plus adrenalectomized rats at time 0 in the presence and absence of atenolol and DuP 753, respectively. In contrast after adrenalectomy alone the AngI levels at time 0, were not different from those of the controls. Subsequently the AngI levels increased at a similar rate as after adrenalectomy in the presence of atenolol. These findings suggest that the increase in plasma Aogen after nephrectomy is essentially mediated by AngII via an adrenal mechanism. It seems likely that this process is triggered by renin released during surgery. The increased renin release after adrenalectomy that is responsible for the increased degradation of Aogen seems not to be mediated by a sympathetic stimulation of the renal beta 1-adrenoceptors.

Serum-free cell culture

Cell culture is one important tool when studying cellular functions and molecular biology. It is also a basic method in most virological investigations. Serum has been an obligatory component in most cell culture media. During the last decades serum-free, chemically defined media have been developed, that are supplemented with a number of substances with specific cellular activities. The main developments of defined media are presented. Examples are given of investigations with different cell types.