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Prolyl hydroxylase and an immunologically related protein (CRP) were purified from neonatal rabbit skin at various time periods following administration of 3H-leucine. The peak incorporation of label into prolyl hydroxylase was found to be 12 hours, while peak incorporation into CRP occurred within 2 hours. Semi-log plots of the loss of radioactivity from these protein pools against time indicated an apparent T 1/2 for prolyl hydroxylase of 78 hours, and a T 1/2 of CRP of 44 hours. Calculated Kd values indicate that that breakdown of active enzyme does not account for the amount of CRP found in tissues.

Prolyl hydroxylase [EC 1.14.11.2] was shown to be inhibited by an ultrafiltrate (less than 30,000 molecular weight) fraction isolated from skin and blood of neonatal and adult rabbits. This fraction also inhibited two other alpha-ketoglutarate requiring mixed function oxidases, lysyl hydroxylase [EC 1.14.11.4] and alpha-butyrobetaine hydroxylase [EC 1.14.11.1] but not the amine oxidase, lysyl oxidase. Purification of the skin ultrafiltrate on Sephadex G-25 demonstrated a peak of prolyl hydroxylase inhibitory activity which chromatographed at a molecular weight corresponding to approximately 3,000. Chromatography of a blood ultrafiltrate separated a similar peak of material which was inhibitory for prolyl hydroxylase.

Industrial workers who are accidentally exposed to cadmium fumes often develop severe lung damage leading to widespread peribronchiolar scarring. This study examined the effect of a single exposure of cadmium chloride aerosol on rat lung lysyl oxidase and prolyl hydroxylase, both markers of connective tissue biosynthesis. Rats were killed at 2, 4, 7, 10, and 21 days after a 2-h exposure to 0.1% Cdcl2 aerosol. Total lung lysyl oxidase was increased 14.8 times that a saline control animals by 4 days and returned to near normal values by 10 days. Interestingly, a small amount of lysyl oxidase activity was also detectable in the lung lavage of unexposed animals and was markedly elevated at the earlier times after cadmium exposure. Total lung prolyl hydroxylase activity paralleled that of lung lysyl oxidase and increased 7.4-fold by the fourth day. A significant increase in total lung hydroxyproline could be demonstrated. Administration of beta-aminopropionitrile, an irreversible inhibitor of lysyl oxidase, prevented much of the increase in lysyl oxidase activity and the accumulation of collagen. The altered tissue amounts of lysyl oxidase and prolyl hydroxylase after cadmium inhalation correlated well with the marked interstitial cell hyperplasia 4 to 5 days after exposure and suggested that connective tissue protein synthesis is activated in the interstitial cell fibroblasts soon after cadmium exposure.

Streptozotocin (STZ)-induced diabetes (8 weeks) produced a marked depressor effect in the spontaneously hypertensive rat (SHR), confirming earlier studies, but had no effect on arterial pressure of normotensive controls (WKY). We investigated the phenomenon further by examining the effects of diabetes on the activities of aortic prolyl hydroxylase (PH) and lysyl oxidase (LO), marker enzymes for collagen biosynthesis, and on the reactivity of isolated mesenteric arteries to vasoactive agents. PH and LO activities of nondiabetic SHR were greater than those of the WKY controls. Diabetes markedly reduced PH and LO activities of SHR aortae, but had no significant effect on PH and LO activities of the WKY strain. The effects of diabetes on vascular collagen biosynthetic enzymes of SHR were not associated with reductions in mesenteric arterial responsiveness or sensitivity to norepinephrine, methoxamine, serotonin or KC1. These results suggest that the depressor effect of diabetes in SHR is associated with a reduction in vascular collagen biosynthesis but not a reduction in vascular reactivity.