The (Na+/K+)-ATPase Activity in the Developing Rat Retina: The Role of Insulin-Like Growth Factor-I (IGF-I)

• Published in: Cellular and molecular neurobiology Vol. 35; no. 2; pp. 243 - 254
• Main Authors: Maturana-Teixeira, Sheila, Braga, Luis Eduardo Gomes, Carpi Santos, Raul, Calaza, Karin da Costa, Giestal-de-Araujo, Elizabeth, Leão-Ferreira, Luiz Roberto
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.03.2015
• Subjects: Biomedical and Life Sciences; Biomedicine; Cell Biology; Neurobiology; Neurosciences; Original Research; IGF-I; Na; ATPase; PKB; Development; Retina; AKT; K
• ISSN: 0272-4340; 1573-6830
• DOI: 10.1007/s10571-014-0119-9

In this work, the (Na + /K + )-ATPase activity was evaluated during the early stages of the postnatal development of rat retina and showed an almost three-time increase from P0 to P14. Expression of the three catalytic subunit isoforms ( α 1, α 2, and α 3) of the (Na + /K + )-ATPase was also evaluated by immunoblot in the same period, but no correlation to the catalytic activity increment was observed. On the other hand, immunolocalization of these three α -catalytic isoforms in the developing retina showed an age-related pattern. Involvement of IGF-I in the stimulation of the (Na + /K + )-ATPase was investigated. Our results demonstrate that the exogenous IGF-I (10 ng/mL) stimulates enzyme activity at the age of P7 only. Incubation of retinas with 10 μM I-OMe-AG 538 (inhibitor of the IGF-I receptor) indicates that the basal (Na + /K + )-ATPase activity is sustained by endogenous IGF-I in P7 animals. These data were corroborated by an age-dependent decrease in the immunodetection of endogenous IGF-I as well as in the phosphorylation level of its cognate receptor in rat retina homogenates. The signaling pathway involved in IGF-I-induced modulation of the (Na + /K + )-ATPase was also investigated. Our data show that the inhibitory effects induced by I-OMe-AG 538 and the PI 3-kinase inhibitor Ly 294002 on the basal (Na + /K + )-ATPase activity were non-cumulative. Furthermore, IGF-I induced phosphorylation of PKB in a Ly 294002-sensitive manner. Together, these data demonstrate that the PI 3-kinase/PKB signaling pathway is involved in the IGF-I-sustained basal (Na + /K + )-ATPase activity during the first 7 days of the postnatal development of rat retina.