The effects of prenatal hypoxia on the levels of the α-subunits of G proteins in the heart of the Broiler chicken (Gallus gallus)

Abstract:

Environmental stress during embryonic development could lead to growth restriction of the embryo, and act as a risk factor for the development of cardiovascular disease in adult life. A common environmental stressor that causes growth restriction is prenatal hypoxia, which has been shown to adversely affect adult health in mammalian models. Prenatal hypoxia causes an increase in catecholamines which results in over stimulation of the cardiac β-adrenergic receptors. Previous work on chickens has shown that prenatal hypoxia causes an increase in the sensitivity of β-adrenergic receptors to epinephrine in the embryonic heart. The sensitivity of these receptors was found to be decreased in prenatal hypoxic juvenile. Prenatal hypoxia has no significant effect on the density of these receptors in neither the embryo nor the juvenile. The lack of change in receptor density implies that the effects of hypoxia are further down stream in the signalling cascade. The β2 adrenergic receptor can couple to both the stimulatory Gα subunit (Gsα) and the inhibitory Gα subunit (Giα). We hypothesized that prenatal hypoxia would cause an increase in the Gsα in the sensitized embryos, while increasing Giα in the desensitized juveniles. This study evaluated the relative levels of Gsα and Giα in the hypoxic chicken embryo, and in the prenatally hypoxic juvenile, Using western blotting. Hypoxia considerably increased Giα in the chicken embryo while having no effect on Gsα. In the prenatally hypoxic juvenile Gsα was significantly increased while no changes were found in Giα. This dissociation between the levels of Gα subunit and receptor sensitivity implies that that hypoxia affects the signaling cascade downstream of the Gα subunit.