Agi ng adversely affects the structure and function of the saliva ry gla nd and leads to ma rked insulin resis t ance that correlates with red uced ins ulin s ignal t ra nsduction, lnsulin-like g rowth factors are k.nown to be regulator involved in embryonic a nd postnatal development with sequences 62% identical t o that of proins ulin , To determine whether i n suli n- like growth facto l' - l, -2, - 1 receptor a l'e involved in the changes in rat salival'y gland by aging, we a na lyzecl the qua nti tation of 19f - 1, -2, - 1 rece ptor mRNA in l'at salivary glancl between 2 weeks and 26 months after bir th using the competiti ve reverse t ra nscriptase-polymerase chain reaction(RT-PCR) methocl Between 2 weeks ancl 2 months age, sharp falls in the qua nt ities of Igf-2 mRNA were observed, W11ereas Igf- 1 receptor mRNA rose by aging, but not sig nifïcantly, The quanti t ies of 19f- l kept by aging, These change seem to be involvecl a role fol' the Igf-2 in sali va ry c1evelopment a ncl earl y growth is incli ca ted, Thus, t he dras tic changes in the qua ntities of Igf-2 mRNA in the ra t sali va ry gla nd by aging seem to be in volved in the development, early growth and homeostasis of sali vary gla nd,

Insulin-like growth factor 2 (Igf-2) and H19 genes are closely linked imprinted genes which have a pivotal role in embryogenesis and fetal development. Igf-2 and H19 are coexpressed in tissues of mesodermal, endodermal and neuroectodermal origin. Rat Igf-2 has a complex structure with three promoters and a complicate imprinting mechanism having an exception of biallelic expression in the choroid plexus, leptomeninges, and fetal tissues of neuroectodermal origin. To detect the expression of maternal and paternal alleles of Igf-2 and H19 during orofacial development, fetal and neonatal hybrid rats, obtained from Wistar and Fisher interstrain rat crosses were used. We also detected the promoter-specificity of Igf-2 transcripts by primers selected from P1, P2, and P3 of Igf-2 gene. RT-PCR analysis of Igf-2 and H19 showed the monoallelic expression of Igf-2 from the paternal allele and H19 from the maternal allele in E15.5 to E19.5 orofaciall structures including the maxilla, tongue, and salivary gland. P3 promoters were active in all tested samples, whereas transcripts derived from P2 promoter arised with approximately half of the tested cases and showed variable alternation. P1 promoter was not transcribed in all tested samples. These results suggest that Igf-2 and H19 may be involved in orofacial development and exhibit parent-of-origin monoallelic expression. On the other hand, in orofaciall development, P2 and P3 promoters except for P1 promoter are transcribed with variable alternative transcripts