Protein kinases, from B to C.

The PKB (protein kinase B) and PKC (protein kinase C) families display highly related catalytic domains that require a largely conserved series of phosphorylations for the expression of their optimum activities. However, in cells, the dynamics of these modifications are quite distinct. Based on experimental evidence, it is argued that the underlying mechanisms determining these divergent behaviours relate to the very different manner in which their variant regulatory domains interact with their respective catalytic domains. It is concluded that the distinct behaviours of PKB and PKC proteins are defined by the typical ground states of these proteins.

Pressor and renal effects of cross-linked hemoglobin in anesthetized cirrhotic rats.

BACKGROUND/AIMS: Cross-linked hemoglobin (XL-Hb), a hemoglobin-based oxygen carrier, is currently under investigation as a blood substitute. In the present study we have evaluated its pressor and renal effects in a rat model of liver cirrhosis by bile duct ligation. METHODS: Experiments were performed 3 weeks after surgery in anesthetized rats In the first protocol, the ability of XL-Hb to recover blood pressure after a hypotensive hemorrhage (0.5 ml/min, 10 min) was analyzed. In the second protocol, the pressor and renal effects produced by the administration of XL-Hb were evaluated during a period of 3 h. RESULTS: After a hypotensive hemorrhage (0.5 ml/min, 10 min), resuscitation with XL-Hb resulted in greater and faster recovery of blood pressure than with the administration of blood. In non-hemorrhaged rats, administration of XL-Hb (5% of blood volume) reversibly increased blood pressure in bile duct ligation and in control rats, but this effect was of longer duration in the control animals. XL-Hb also induced brisk increases in water and sodium excretion in both groups of animals, but the response of the control animals was more intense and sustained than that of the bile duct ligation rats. Glomerular filtration rate and renal blood flow showed slight decreases, but they were well maintained around the baseline levels. All the parameters studied were normalized 3 h later. In additional experiments, the effect of a bolus of L-NAME (10 mg/kg), an inhibitor of nitric oxide synthase, 1 h after the administration of XL-Hb was partially reduced, suggesting that the effect of XL-Hb may be secondary to the disappearance of circulating nitric oxide. CONCLUSIONS: XL-Hb seems to be effective as a resuscitative solution in case of hemorrhage in cirrhotic rats Moreover, this blood substitute only moderately and reversibly elevates blood pressure and does not adversely affects renal function.