A novel compound JPM8: in vivo penile activity promotion in rats, effect on the relaxation and cGMP/cAMP accumulation in isolated rabbit corpora cavernosa.

JPM8 is a novel sildenafil-like PDE5 inhibitor. Its efficacy was tested in vivo by the oral administration of drugs to a rat model and recording penile activity changes. Effect on the relaxation of the rabbit cavernosa was tested in vitro using an organ bath were drugs are added to the tissue media and relaxation was recorded using a transducer connected to a chart recorder. The accumulation of cGMP and cAMP was measured by incubation of cavernosa strips and then extracting the produced cGMP and cAMP in the incubation mixture, then quantitating it using ELISA. JPM8 showed increased and promoted sexual and penile activity in rats in a similar but slightly higher trend than the positive control sildenafil. JPM8 was more efficient in relaxing the rabbit corpora cavernosa than sildenafil. The cGMP and cAMP accumulation showed a similar trend for both drugs. We concluded that JPM8 was very effective in promoting sexual activity in rats, relaxing the corpora cavernosa and promoting cGMP accumulation in rabbits.

Ferula harmonis 'zallouh' and enhancing erectile function in rats: efficacy and toxicity study.

Ferula harmonis, which is locally called 'zallouh' in the Middle East, is used as an aphrodisiac as it is reputed to enhance male sexual behavior, however, there is no scientific verification. In this study, the oil extracted from the seeds of Ferula harmonis was tested for its efficacy in enhancing erectile function and toxicity in male rats. The sexual activities assessed by penile erection index were dose dependent. The ED(50) (12.03 mg/kg) was 880 times less than the LD(50) (10.6 g/kg). However, when doses ranging from 0.05, 0.5 to 2 g/kg were given daily for 28 days, acute and subacute toxicity were observed. There was a decrease in total body weight, hepatomegaly, atrophic testis, significant decrease in hemoglobin and red blood cell count. In addition, there was a significant decrease in cholesterol level. All the above indicate that the crude oil from the plant Ferula harmonis can enhance erectile function, however, it becomes toxic if it is used for a long period of time. Further studies are underway to isolate and identify the active ingredients and their exact mechanisms of action.

Refolding and recognition of mitochondrial malate dehydrogenase by Escherichia coli chaperonins cpn 60 (groEL) and cpn10 (groES).

In vitro refolding of pig mitochondrial malate dehydrogenase is investigated in the presence of Escherichia coli chaperonins cpn60 (groEL) and cpn10 (groES). When the enzyme is initially denatured with 3 M guanidinium chloride, chaperonin-assisted refolding is 100% efficient. C.d. spectroscopy reveals that malate dehydrogenase is almost unfolded in 3 M guanidinium chloride, suggesting that a state with little or no residual secondary structure is the optimal 'substrate' for chaperonin-assisted refolding. Malate dehydrogenase denatured to more highly structured states proves to refold less efficiently with chaperonin assistance. The enzyme is shown not to aggregate under the refolding conditions, so that losses in refolding efficiency result from irreversible misfolding. Evidence is advanced to suggest that the chaperonins are unable to rescue irreversibly misfolded malate dehydrogenase. A novel use is made of 100 K Centricon concentrators to study the binding of [14C]acetyl-labelled malate dehydrogenase to groEL by an ultrafiltration binding assay. Analysis of the data by Scatchard plot shows that acetyl-malate dehydrogenase, which has previously been extensively unfolded with guanidinium chloride, binds to groEL at a specific binding site(s). At saturation, one acetyl-malate dehydrogenase homodimer (two polypeptides) is shown to bind to each groEL homooligomer with a binding constant of approx. 10 nM.

A 1H-NMR study of the interactions between rat tissue kallikrein and two peptide inhibitors.

The 1H-NMR spectra have been obtained for rat submandibular kallikrein in the absence and presence of inhibitors. Two competitive inhibitors were investigated, the tripeptide leupeptin (a potent inhibitor with Ki 0.5 microM) and a hexapeptide (a much weaker, substrate-analogue inhibitor with Ki 380 microM). Analysis of the NMR spectra showed that binding of leupeptin to kallikrein led to a change in the conformation of the enzyme, whereas binding of the substrate analogue to the enzyme produced no such change and may have resulted in a conformational change of the inhibitor.

Characterization of kallikrein isolated from rat submandibular glands by a simple and rapid purification procedure.

Numerous biochemical properties (e.g. Mr, carbohydrate content, pI) were determined for kallikrein isolated from rat submandibular glands by a simple, rapid purification procedure. The kinetic behaviour of the enzyme towards various inhibitors and synthetic substrates was investigated. The effects of different salts and detergents on the esterolytic activity of the rat tissue kallikrein were recorded.

A simple and rapid purification of kallikrein from rat submandibular gland.

Rat submandibular kallikrein was isolated in an 87% yield by a very quick and simple procedure involving hydrophobic interaction chromatography. Furthermore, that purification method was superior to both aprotinin-affinity chromatography and immunoaffinity chromatography for the purification of rat submandibular kallikrein. The kallikrein purified by hydrophobic interaction chromatography consisted of a number of isoenzymes. The major component of Mr 38,000 seen on SDS-gel electrophoresis was found to be the glycosylated kallikrein, whereas the minor component of Mr 26,000 represented the non-glycosylated enzyme.