Enzymes In Rat Lung Research Articles

The enzymatic conversion of arachidonic acid into 8,11,12-trihydroxyeicosatrienoic acid Resolution of rat lung enzyme into two active fractions

The conversion of arachidonic acid into 8,11,12-trihydroxyeicosatrienoic acid by rat lung high-speed supernatant has been resolved into two separate stages through ammonium sulfate precipitation. The first stage is catalysed by 0–30% ammonium sulfate fraction and converts arachidonic acid and 12-hydroperoxyeicosatetraenoic acid into an intermediate X. X is subsequently utilized in the second stage by the fraction sedimented at 30–50% saturation in ammonium sulfate to form two isomeric 8,11,12-trihydroxy-eicosatrienoic acids.

Induction of angiotensin I-converting enzyme in rat lung with captopril: The effect of adrenalectomy

In spontaneously hypertensive rats, treatment with captopril, 0.2 g/liter of drinking fluid for 12 to 24 weeks, caused a threefold increase in serum angiotensin I-converting enzyme activity. Angiotensin I-converting enzyme increased 25 to 120 percent in lung plasma membranes. The elution profile of angiotensin I-converting enzyme on DEAE cellulose and after gel filtration on Sepharose 4B was unchanged by captopril. The K m value also remained unchanged. In Wistar rats subjected to bilateral adrenalectomy, treatment with the same dose of captopril for 3 days resulted in increased serum angiotensin I-converting enzyme activity in both sham-operated and adrenalectomized rats, but angiotensin I-converting enzyme concentration increased in lung plasma membranes from sham-operated rats and captopril-treated rats only. We conclude that captopril causes induction of angiotensin-converting enzyme biosynthesis in spontaneously hypertensive and Wistar rats. The change is a quantitative one. Intact adrenal glands may be important for the incorporation of angiotensin I-converting enzyme into lung membranes.

Complex competitive and non-competitive inhibition of rat lung angiotensin-converting enzyme by inhibitors containing thiol groups: captopril and SA 446.

1. The kinetics of the inhibitory action of four different angiotensin-converting enzyme inhibitors was evaluated in vitro with rat lung enzyme and the substrate hippuryl-histidyl-leucine. 2. Enzyme velocity against substrate concentration curves were fitted squares to hyperbolae by a weighted least squares iterative method to obtain apparent values of Km, Vmax. and K/V at each concentration of inhibitor. 3. The inhibitory constants Ki and Ki' were obtained by weighted linear regressions of K/V against i and 1/V against i respectively. 4. Teprotide was the least potent inhibitor with a Ki of near 20 nmol/l whereas captopril (SQ 14 225) and SA 446 were both approximately 10 times and MK 421 approximately 20 times more potent. 5. Two inhibitors which lacked thiol groups [teprotide or SQ 20 881 and N-(1-S-1-carboxy-3-phenylpropyl)-L-Ala-L-Pro or MK 421] produced a purely competitive pattern of inhibition with increased apparent Km but no change in apparent Vmax.. 6. Two inhibitors containing thiol groups [captopril or SQ 14 225 and 2-(2'-hydroxyphenyl)-3-(3-mercaptopropanoyl)-4-thiazolidine carboxylic acid or SA 446] both produced a mixed competitive and non-competitive pattern of inhibition with increased apparent Km and decreased Vmax.. 7. It is possible that thiol-containing inhibitors might produce non-competitive inhibition of converting enzyme by forming strong bonds with zinc near the active site of the enzyme.

Induction of angiotensin I-converting enzyme in rat lung with captopril (SQ 14225)

Angiotensin I-converting enzyme (ACE, EC 3.4.15.1.) was measured in serum and in pulmonary plasma membranes of 140 spontaneously hypertensive rats (SHR, Okamoto Aoki strain), divided into 4 groups, and treated with SQ 14225 (Captopril®), 0.2 mg · ml −1 in drinking water, for 0–24 weeks. Serum ACE activity increased 2.5–3 fold after 12–24 weeks of SQ 14225 treatment, paralleled by an increasep of ACE concetration in purified pulmonary plasma membranes (25–52%), and in ACE concentration upon solubilization with Triton X-100 from such plasma membranes (96–120%). We conclude that the ACE inhibitor, SQ 14225, causesp marked induction of pulmonary ACE biosynthesis. High serum ACE activity probably reflects increased total biosynthesis of the enzyme.

Mechanisms and regulation of biosynthesis of saturated fatty acids.

Mechanisms and regulation of biosynthesis of saturated fatty acids.

Cigarette smoke: Stimulatory effect on metabolism of 3,4-benzpyrene by enzymes in rat lung

The enzymatic hydroxylation of 3,4-benzpyrene (BP) by lung was increased 34% and 186% in rats exposed to cigarette smoke for 2 or 4 hours, respectively. Induction of BP-hydroxylase in lung by cigarette smoke was completely blocked by actinomycin D or puromycin. An increase in BP-hydroxylase activity was also observed in various organs of pregnant rats exposed to cigarette smoke 5 hours daily for 3 days. The most marked increases were observed in the lung (12-fold) and placenta (4-fold), although increases were also observed in the intestine and in maternal and fetal liver.

Effect of food and water deprivation on surface activity of lungs of rats.

Effect of food and water deprivation on surface activity of lungs of rats.