Unique pattern of cleavage of vasoactive intestinal peptide by human lymphocytes.

Human cultured T lymphocytes of the Jurkat line and myeloma cells of the U266 line cleaved the 28 amino acid vasoactive intestinal peptide (VIP1-28) preferentially at three sites with time- and temperature-dependence. The fragments VIP4-28 and VIP23-28) from an endopeptidase activity, and VIP15-28 from a trypsin-like peptidase, together represented a range of 26-65% of the VIP1-28 recovered after 2 hr at 37 degrees C or 4 hr at 22 degrees C, based on the absorbance of purified peptides and the radioactivity of [125I]Tyr10 VIP1-28. The endopeptidase activity was associated with membranes recovered after disruption of U266 cells by nitrogen cavitation. Pretreatment of intact U266 and Jurkat cells with diisopropylfluorophosphate (DFP) and the subsequently isolated subcellular particles with phenylmethylsulphonylfluoride (PMSF) and leupeptin inhibited the trypsin-like enzyme by a mean of 80%, without suppressing endopeptidase activity. In contrast, 0.1 mM DL-thiorphan and phosphoramidon blocked selectively a range of 35-70% of the endopeptidase activity in membrane preparations and intact cells. The capacity of lymphocytes to degrade VIP1-28 may substantially alter the effects of this neuromediator on functions of some subsets of T and B cells.

Distinct subsets of somatostatin receptors on cultured human lymphocytes.

Somatostatin (SOM) is a neuroendocrine tetradecapeptide that suppresses specific functions of differentiated T-cells and antibody-producing cells. The Jurkat line of human leukemic T-cells and U266 IgE-producing human myeloma cells bound [I-Tyr11]SOM specifically. The maximal level of specific binding was attained by 1-2 h at 22 degrees C for both types of cells and reversed by 70-85% within 2-3 h after the addition of excess nonradioactive SOM. Computer-assisted Scatchard analysis of the competition curves revealed two classes of binding sites for both cells. An average of 144 and 1295 high affinity receptors per Jurkat and U266 cells had a Kd value of 3 pM and 5 pM, respectively, whereas a large number of low affinity sites had Kd values of 66 nM and 100 nM. The affinity of the analogs somatostatin 28, [I-Tyr11]SOM, and [D-Trp8, D-Cys14]SOM for Jurkat and U266 cell lines, relative to SOM, suggested a degree of specificity similar to receptors on neuroendocrine cells.

Smoke inhalation model for lung permeability studies.

The purpose of this project was the development of a small animal model and the use of external gamma imaging for the study of acute post-inhalation permeability changes. New Zealand white rabbits were anesthetized with ketamine and acepromazine IM, intubated, and a catheter placed in an ear artery. Smoke was produced by burning absorbent cotton in a combustion chamber supplied with 10 liters/min of air. Smoke was delivered to a holding chamber, allowed to cool to room temperature, and immediately delivered to the animals via endotracheal tube. Animals were allowed to inhale smoke for 3 sessions of 2 to 3 minutes. Blood samples were collected for the measurement of PO2, PCO2, and COHb. Lungs were removed at 3 to 4 days postinjury and subjected to microscopic histologic analysis. The results of six animal experiments showed a significant inhalation injury. The mean COHb level was 48% (range, 36%-58%). The change in the pre- and post-injury PO2 and PCO2 values were not significant (mean PO2, 66 mm Hg; mean PCO2, 32 mm Hg). Histologic evaluation of the lungs of three animals at 24 hrs postinjury revealed extensive loss of tracheal epithelium extended to many terminal bronchi. Inflammation of surrounding tissue, including edema and increased migration of polymorphonuclear cells, was also present. Analysis of tissue obtained at 10 to 14 days showed reparative reepithelialization of trachea and major bronchi but acute inflammation and loss of intralobar bronchi. Inflammatory exudate extended to adjacent alveoli. In conjunction with the above model we have developed a method for the noninvasive measurement of lung permeability changes.(ABSTRACT TRUNCATED AT 250 WORDS)