No effect of growth hormone treatment on axonal transport of slow component a in diabetic and nondiabetic rats.
A decreased axonal transport of slow component a (SCa), i.e., neurofilaments, is an early event in experimental diabetes as well as hypothyroidism, and common to these metabolic derangements are decreased levels of serum insulin-like growth factor I (IGF-I). To evaluate the possible connection between these facts, we investigated the effect of growth hormone (GH), which stimulates IGF-I production, on axonal transport of SCa in diabetic and nondiabetic rats. Serum concentrations of IGF-I fell from about 1500 micrograms/L in controls to about 600 micrograms/L in diabetics. GH treatment (100 mu/rat twice daily) normalized IGF-I for the first week of diabetes, after which the level decreased to the level of the untreated diabetics. The SCa transport velocity was found to be decreased in the diabetic nerves as previously reported [0.91 +/- 0.07 = mm/day, n = 9; (mean +/- SD) versus 1.01 +/- 0.09 mm/day, n = 8, in controls, 2 p less than 0.05). No changes were seen for the GH-treated groups (1.03 +/- 0.06 mm/day, (n = 11) in GH-treated controls). The lack of effect of GH treatment can be due to blockage of IGF-I synthesis or the decreased level of thyroid hormone, triiodothyronine (T3), in the diabetic rats.
Sidenius
P
P
Department of Neurology, Hvidovre Hospital, Denmark.
Braendgaard
H
H
Flyvbjerg
A
A
D000704:Analysis of Variance; D000818:Animals; D001370:Axonal Transport / Q000187:drug effects*; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D005727:Ganglia, Spinal / Q000187:drug effects / Q000503:physiopathology*; D013006:Growth Hormone / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013974:Thyroxine / Q000097:blood*; D014284:Triiodothyronine / Q000097:blood*
D001786:Blood Glucose; D014284:Triiodothyronine; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D013974:Thyroxine