Kidney insulin-like growth factor-I mRNA levels are increased in postpubertal diabetic rats.
Diabetes-associated renal enlargement is more marked in postpubertal than prepubertal rats, and in the postpubertal rat, is associated with increased kidney insulin-like growth factor-I (IGF-I) levels for the first 2 days. In order to determine whether local IGF-I production is the cause of this increase in tissue levels, IGF-I mRNA levels were determined in pre- and postpubertal Sprague-Dawley rats made diabetic with streptozotocin (STZ) and in control rats. RNA was extracted from kidneys and livers of rats at 0 h, 6 h, 12 h and days 1, 2, 3 and 7 after STZ injection. After Northern blotting and hybridization with an oligonucleotide probe complementary to an E domain of the IGF-I cDNA, four distinct bands (7.4, 4.8, 1.8 and 1.0 kb) were found. Densitometric analyses of the most prominent bands (7.4 and 1.0 kb), after normalization for 18S ribosomal RNA content, revealed a 50-100% increase in the kidneys of postpubertal diabetic rats compared with postpubertal controls 12 h after STZ injection (P less than 0.05, diabetes vs control). Between days 2 and 7, kidney IGF-I mRNA levels in postpubertal diabetic rats fell to approximately 50% of control levels (P less than 0.05, diabetes vs control). In contrast, kidney IGF-I mRNA levels in the prepubertal diabetic rats remained unchanged over the 7 days. Liver IGF-I mRNA levels did not rise during the first 24 h and fell to approximately 60% of control levels by day 7 in both pre- and postpubertal diabetic rats (P less than 0.05, diabetes vs control). Increased local IGF-I production may underlie the initiation of renal enlargement associated with diabetes mellitus.
Bach
L A
LA
Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg, Victoria, Australia.
Stevenson
J L
JL
Allen
T J
TJ
Jerums
G
G
Herington
A C
AC
D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D015342:DNA Probes; D003921:Diabetes Mellitus, Experimental / Q000235:genetics*; D015870:Gene Expression / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007668:Kidney / Q000737:chemistry / Q000502:physiology*; D008099:Liver / Q000737:chemistry / Q000502:physiology; D008297:Male; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D012741:Sexual Maturation / Q000235:genetics*
D015342:DNA Probes; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I