ONTOGENY OF GTP-BINDING PROTEINS, G(1) AND G(0), IN RAT RETINA

The distribution and the levels of G(i1) (plus G(i3)), G(i2), and G(o) in rat retina were studied immunohistochemically and immunochemically during development. At embryonic day (E) 15, G(i1)alpha/G(i3)alpha wa s observed in the inner layer of the neural retina, the future nerve f iber layer (NFL), while G(i2)alpha was observed both in the inner and outer layers of the neural retina. No immunoreactivity for G(o) alpha was observed. At E18, G(i1)alpha/G(i3)alpha and G(i2)alpha appeared in the inner plexiform layer (IPL), while G(o) alpha was faintly immunor eactive only in the NFL. At birth, G(i2)alpha/G(i3)alpha and G(o) alph a appeared in the ganglion cell layer. G(i2)alpha was intensely immuno reactive in the NFL and IPL. At postnatal day (P) 10, the inner portio ns of the retina, from the NFL to the outer plexiform layer, were immu noreactive to G(i1)alpha/G(i3)alpha, G(i2)alpha, and G(o) alpha. G(i1) alpha/G(i3)alpha and G(o) alpha were distributed characteristically in a laminated pattern in the IPL, but G(i2)alpha was present homogeneou sly in the IPL. At P12, G(i2)alpha appeared in the outer nuclear layer . As the postnatal days advanced, the laminated pattern of immunoreact ivity to G(o) alpha in the IPL became diffuse, but immunoreactivity to G(i1)alpha/G(?)(i3)alpha remained. The results of enzyme immunoassays showed that the concentration of G(o) alpha increased rapidly from P1 0 to P15 and reached almost the adult level at P20-P30, while G(i2)alp ha decreased until P15 and was almost constant thereafter. These resul ts showed that the distribution of G(i1)alpha/G(i3)alpha, G(i2)alpha, and G(o) alpha differs during development, suggesting that each G prot ein in the developing retina has a unique function.