At least one mechanism is from glucocorticoid receptor effects.
Evidence towards this:
Fed Proc. 1984 Oct;43(13):2793-8.
Effect of topically applied steroidal and nonsteroidal anti-inflammatory agents on skin repair and regeneration.
Alvarez OM, Levendorf KD, Smerbeck RV, Mertz PM, Eaglstein WH.
We studied the effects of topically applied steroidal and nonsteroidal anti-inflammatory agents on dermal and epidermal wound healing. Superficial wounds (0.3 mm deep) on the skin of domestic pigs were treated daily with either 0.1% triamcinolone acetonide (TA), 1% hydrocortisone (HC), 1% nandrolone decanoate (ND), 1% ND + 0.1% TA, 10 mg ibuprofen, 10 mg meclofenamate sodium, 3 mg indomethacin, vehicle (USP petrolatum or 70% ethanol), or control (untreated). Wounds were excised on days 2-7 after wounding and the epidermis was separated from the dermis. The dermis was assayed for collagen biosynthesis and the epidermis was evaluated for reepithelialization. A significant decrease (P less than 0.01) in relative collagen synthesis was observed in the wounded dermis in both HC- and TA-treated groups on day 3 after wounding,
(corticosteroids decreased collagen synthesis)
but there were no significant differences on days 4-7. Depressed collagen and noncollagenous protein production was also noted in vehicle-treated wounds on day 3. Topical application of ND did not affect collagen synthesis,
(note the above)
but when combined with TA it eliminated the inhibitory effect observed as a result of TA alone.
(in other words, it countered the adverse effect of the added corticosteroid, but apparently made no significant difference with the physiological levels of the pigs.)
Topical ND accelerated wound reepithelialization by 12.5% compared with vehicle and by 26% compared with untreated controls. TA delayed epidermal resurfacing by 22%, but when combined with ND (ND + TA) the rate of reepithelialization was similar to vehicle-treated wounds. HC enhanced resurfacing when compared with untreated wounds but did not differ markedly from its vehicle. The nonsteroidal anti-inflammatory drugs when topically applied markedly reduced inflammation (erythema, heat, and edema) but did not influence the healing process.
As an example of the sort of thing cited to claim nandrolone enhances collagen synthesis:
Sichuan Da Xue Xue Bao Yi Xue Ban. 2004 Jul;35(4):508-11.
[Effects of nandrolone phenylpropionate on fibroblasts after injury in rats]
[Article in Chinese]
Cen Y, Liu N, Liu XX, Li K.
Department of Burn and Plastic Surgery, West China Hospital, Sichuan University, Chengdu 610041, China.
OBJECTIVE: To explore the effects of nandrolone phenylpropionate (NP) on fibroblasts after injury in rats. METHODS: Thirty-two Wistar rats with a deep second-degree scald injury and 20% total body surface area were randomly divided into two groups to receive either 5 mg/kg NP (NP group) or normal saline as placebo (control group) every other day. Integrated optical density (IOD) of androgen receptor (AR) and mRNA expression level of alpha1 (I) procollagen were measured by immunohistochemistry and quantitive fluorescent RT-PCR individually on the post-burn days 4, 7, 14 and 21. Fibroblasts were isolated from granulation tissue of a Wistar rat and were cultured in RPMI1640 with the addition of NP at different concentrations. Cell viability of fibroblasts was measured by MTT test, and the proliferative index, by flow cytometry (FCM). RESULTS: (1) Compared with the A value of the concurrent control group, higher A values were seen in NP groups containing different concentrations of NP, and significant difference of proliferative index was observed in NP group, P<0.05. (2) The expression of alpha1 (I) procollagen mRNA in NP groups was much higher than that in control groups. A significant difference between the two groups was noted on the post-burn days 7, 14 and 21, P<0.05, but no difference was seen on day 4. (3) The density of AR on fibroblasts in NP group was higher than that in control group at each time point. And a positive correlation between the expression of alpha1 (I) procollagen mRNA and the quantity of AR on fibroblasats was confirmed (r = 0.836). CONCLUSION: Nandrolone phenylpropionate could promote fibroblast replication, increase the mRNA level of alpha1 (I) procollagen and enhance the density of AR on fibroblasts.
But as for claims of stanozolol slowing collagen synthesis:
J Invest Dermatol. 1998 Dec;111(6):1193-7.
Stimulation of collagen synthesis by the anabolic steroid stanozolol.
Falanga V, Greenberg AS, Zhou L, Ochoa SM, Roberts AB, Falabella A, Yamaguchi Y.
University of Miami School of Medicine, Department of Dermatology, Miami Veterans Affairs Medical Center, Florida, USA.
There is evidence that anabolic steroids, which are derived from testosterone and have markedly less androgenic activity, promote tissue growth and enhance tissue repair; however, the mechanisms involved in their anabolic activities remain unclear. In this report, we measured the effect of the anabolic steroid stanozolol on cell replication and collagen synthesis in cultures of adult human dermal fibroblasts. Stanozolol (0.625-5 microg per ml) had no effect on fibroblast replication and cell viability (p = 0.764) but enhanced collagen synthesis (p < 0.01) in a dose-dependent manner (r = 0.907). Stanozolol also increased (by 2-fold) the mRNA levels of alpha1 (I) and alpha1 (III) procollagen and, to a similar extent, upregulated transforming growth factor-beta1 (TGF-beta1) mRNA and peptide levels (p < 0.001). There was no stimulation of collagen synthesis by testosterone. The stimulatory effects of stanozolol on collagen synthesis were blocked by a TGF-beta1 anti-sense oligonucleotide, by antibodies to TGF-beta, and in dermal fibroblast cultures derived from TGF-beta1 knockout mice. We conclude that collagen synthesis is increased by the anabolic steroid stanozolol and that, for the most part, this effect is due to TGF-beta1. These findings point to a novel mechanism of action of anabolic steroids.
As for claims of different percent values, there is no way that anabolically-equivalent doses were being compared, except perhaps by the purest freak chance. So no seriousness should be given to the figures or differences between them.