Partial sequencing and tissue distribution of the canine isoforms of steroid 5?-Reductase type I and type II

Identification of 5α‐reductase isoenzymes in canine skin

“…We have shown for the first time, to the best of the authors' knowledge, that 5αR1 and 5αR3 – but not 5αR2 – are expressed in the skin of healthy dogs. Previous studies have identified the isoforms 5αR1 and 5αR2 in the prostate, adrenal gland, cerebellum, cerebrum, liver, testis, cardiac muscle, bladder wall, lung and pectoral muscle of dogs . Our finding of mRNA encoding 5αR1 and 5αR3 in canine skin is consistent with studies in humans, in which 5αR3 is the predominant isoenzyme detected and 5αR2 levels are low in comparison to the other isoenzymes .…”

“…The two predominant inhibitors used in the treatment of AGA in humans are finasteride and dutasteride . Their use in dogs for treatment of alopecia has not been reported, although they are used in dogs to treat prostate cancer . Both compounds inhibit 5αR1 and 5αR2 activities; finasteride is selective for 5αR2 and dutasteride is selective for 5αR1 and 5αR2.The ability of these drugs to inhibit 5αR3 is not clear, as one study showed potent inhibition of 5αR3 activity by dutasteride in HEK293 cells stably expressing this gene, whereas another study demonstrated that dutasteride did not effectively inhibit exogenous 5αR3 activity in a hamster ovary cell line .…”

Selective non-steroidal inhibitors of 5α-reductase type 1

“…In this case it is important to know if the enzyme or receptor of the species used is similar to the human counterpart. As regard the 5␣R system many species, including mice, rats dogs and monkeys possess two 5␣R genes [80][81][82][83][84]. The panspecific distribution and duplication of the enzyme in mammals underscore the need of DHT for androgen action.…”

Discovery of a novel hybrid from finasteride and epristeride as 5α-reductase inhibitor

“…There are two isoforms of human 5-AR identified as type I and type II. [4][5][6] In normal human skin the type I reductase is the predominant type expressed, whereas 5-AR type II is the major form found in the prostate. 7 Finasteride 1 is a selective inhibitor of the type I and type II isoforms of steroid 5-AR.…”