Characteristics and distribution of specific binding sites for leukotriene C4 in human bronchi

The binding of [3H]leukotriene (LT) C4 to membranes from human bronchi has been characterized. The specific binding, measured at 4 degrees C, was very rapid, equilibrium being attained within 1 to 5 min. The binding was also rapidly reversible and saturable (maximum binding = 187 pmol/mg of protein). LTC4, LTD4, LTE4 and the LT antagonist FPL 55712 competed with [3H]LTC4 for its binding sites, with the following IC50 values: 0.12; 2.3; 30; and 20 microM. Therefore, the binding sites displayed a higher affinity for LTC4 than for the other sulfidopeptide LTs. Computer-assisted analysis of either the saturation or the competition curves for LTC4 indicated the existence of two classes of binding sites with different affinities (Kd1 and Kd2 = 70 nM and 0.58 microM, respectively), in agreement with the curved semilog plot of the dissociation time course. CaCl2 or MgCl2 increased and GTP or 5'-guanylylimidodiphosphate did not decrease the specific binding. In addition, the distribution of the binding sites for [3H]LTC4 along the human respiratory tree was investigated. At a fixed (10 nM) [3H]LTC4 concentration, membranes obtained from bronchi removed at different levels of the airway tree did not bind LTC4 in a significantly different amount. This is compatible with the finding that LTC4 receptors should be present on bronchi of various caliber, as both small and large airways respond to LTs.

Effect of the beta-2 adrenergic agonist fenoterol on the release of leukotrienes and prostaglandin D2 from human lung parenchyma

Ca++-ionophore and antigen challenge of human lung fragments caused a massive release of leukotrienes, whose relative proportions varied considerably and were dependent on the experimental conditions. A broncho-selective beta 2-adrenoceptor agonist fenoterol was able to prevent the antigen-induced leukotriene release completely, whereas the Ca++-ionophore induced leukotriene release was only moderately inhibited. The HPLC data were confirmed by SRS-A bioassay.

Release of leukotrienes, induced by the Ca++ ionophore A23187, from human lung parenchyma in vitro

When chopped human lung is stimulated with the Ca++ ionophore A23187 (0.25-10 microM) leukotriene (LT) B4, LTD4 and LTE4 are found in the incubation medium according to different patterns. LTD4 is released promptly and its levels increase up to 45 min after the stimulus (A23187, 10 microM) and decline later (120 min); LTE4 formation follows a sigmoidal shape and continues to accumulate even 2 hr after the challenge; LTB4 levels reach a plateau at 45 min. LTC4 was undetectable in most experiments but it was found to accumulate when reduced glutathione (10 mM) was added. Addition of exogenous LTC4 to unstimulated fragments of human lung shows that an effective interconversion to LTD4 and LTE4 takes place: A23187 stimulates formation of LT and cyclo-oxygenase products dose dependently; a statistically significant formation of LT occurs at A23187 concentration of 1 microM whereas thromboxane B2 (TXB2) and 6-K-prostaglandin F1 alpha levels increased significantly only at 2.5 microM A23187. Pretreatment with U-60257 (100 microM) prevented formation of LT without a concomitant increase of TXB2 levels. Indomethacin (1.5 microM) blocked the release of 6-K-prostaglandin F1 alpha and TXB2 without a shift of arachidonic acid towards LT-like activity. Addition of exogenous LTC4 did not trigger synthesis of TXB2 or 6-K-prostaglandin F1 alpha. Our results indicate that reduced glutathione levels and the activity of the enzymes involved in LT biosynthesis and/or metabolism play an important role in controlling the pattern of LT release from human lung.

Autologous blood predeposit for elective surgery: a program for better use and conservation of blood

We report the results of a pilot study on predeposit autotransfusion for elective surgery. In 2 years 319 U, each consisting of 350 ml of blood, were donated by 206 patients. Each patient gave 1, 2, or 3 U according to hematocrit levels within 10 days of undergoing surgery on the gastrointestinal tract, lung, liver, kidney, brain, thyroid, arteries, or breast. A hemoglobin drop of about 0.8 gm/dl occurred after each blood donation. A total of 259 autologous and 128 homologous U were transfused to 166 patients during surgery or within postoperative day 4; 40 patients required no blood transfusion. About 70% of patients did not need homologous blood products in addition to autologous units. The most active team of surgeons and anesthesiologists covered about 40% of the patients' blood needs during the study period with autologous units. No patient experienced untoward reactions before, during, or after surgery. Surgeons' and anesthesiologists' responses to the program improved during the study as soon as the advantages of the procedure became clearer. However, gentle pressure from the Transfusion Center was essential for the program's expansion. The patients' acceptance was excellent. We conclude that predeposit autotransfusion is a safe and feasible procedure for transfusion treatment in elective surgery.

[Extra-hospital emergencies. Proposal for a regional aid plan for Northern Lombardy and adjacent areas using helicopters]

An aid service based on the use of helicopters for Northern Lombardy and its adjacent areas is proposed. This would be based on the Varese Hospital and on existing heliports and airports in the area, this being one of Europe's most heavily populated and industrialised regions. The question of airborne aid is discussed, together with the solutions adopted in Italy, and those proposed and partly put into effect in Italy. An examination is also made of the factors in favour of the placement proposed; geographical features, road infrastructures, distances, prevailing weather conditions, and other points. The proposal is seen as a working hypothesis available for the authorities responsible under the current legislation, and as a model for similar investigations in other areas.