Biochemical factors involved in the FSH action on amino acid transport in immature rat testes.
Testes of 15-day-old rats preincubated and incubated during different times with various doses of FSH (0.2; 2.0 and 20.0 mU/ml) in Krebs-Ringer bicarbonate (KRb) buffer increase the uptake of [14C] methylaminoisobutyric acid and [14C] aminoisobutyric acid. The basal and FSH stimulated amino acid transport occurs at absolute lower levels when the protein or glycoprotein synthesis is inhibited by cycloheximide (350 mumol/l) or tunicamycin (12 mumol/l) or when the microtubules are depolymerized with colchicine (1.2 mumol/l). However, the proportional increase of amino acid transport produced by FSH was maintained. The blockage of the voltage-dependent Ca++ channels with verapamil or the competitive inhibition of the bivalent ion channels by Co++ or Ni++ nullified the stimulatory action of FSH on the amino acid transport. Also quinine, that blocks the ATP dependent K+ channels, abolished the FSH action. It was concluded that in immature rat testes FSH stimulates amino acid transport through a mechanism involving voltage-dependent Ca++ channels and ATP-sensitive K+ channel.
Wassermann
G F
GF
Center of Experimental Endocrinology, UFRGS, Porto Alegre, Brazil.
Bloch
L M
LM
Grillo
M L
ML
Silva
F R
FR
Loss
E S
ES
McConnell
L L
LL
D000596:Amino Acids / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D001693:Biological Transport, Active / Q000502:physiology; D015220:Calcium Channels / Q000378:metabolism; D005640:Follicle Stimulating Hormone / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D008870:Microtubules / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013737:Testis / Q000378:metabolism*
D000596:Amino Acids; D015220:Calcium Channels; D015221:Potassium Channels; D011500:Protein Synthesis Inhibitors; D005640:Follicle Stimulating Hormone