Protocollagen proline hydroxylase activity in experimental pulmonary fibrosis of rats.

Abstract

Abstract The activity of the enzyme protocollagen proline hydroxylase which synthesizes the hydroxyproline in collagen by hydroxylating proline in protocollagen was determined in rat lung tissue. About 80 per cent of the enzyme activity was recovered in the 100,000 × g supernatant fraction of the lung homogenate, and the enzyme required ascorbic acid, α-ketoglutarate, and ferrous iron for its activity. When ferrogluconate (100 mg. per kilogram per day) was injected into rats for 10 days, the enzyme activity increased into 134 per cent of the control value. Injections of ascorbate (100 mg. per kilogram per day) or cortisone (20 mg. per kilogram per day), or administration of d-penicillamine (200 mg. per kilogram per day) in drinking water did not change the enzyme activity. The protocollagen proline hydroxylase activity was determined in the lung tissue of rats with experimental silicosis induced by an intratracheal injection of silica dust. The enzyme activity was increased at 5 weeks in silicotic rats and reached a maximum, 259 per cent of the control value, at 16 weeks after the induction of silicosis. The enzyme activity was increased before fibrosis could be demonstrated by means of histological staining or chemical hydroxyproline analyses.