ABSTRACT
1. The beta2-agonist salmeterol is a potent relaxant of airway smooth muscle with a long duration of action. Previous studies of cyclic AMP accumulation, however, have indicated that salmeterol is a low efficacy beta2-agonist when compared to isoprenaline. Here we have compared the properties of salmeterol and isoprenaline as stimulants of gene transcription in CHO-K1 cells transfected with the human beta2-adrenoceptor to different levels (50 and 310 fmol mg protein(-1)). 2. Gene transcription was monitored using a secreted placental alkaline phosphate (SPAP) reporter gene under the transcriptional control of six cyclic AMP response element (CRE) sequences. 3. In the lower expressing cells (CHO-beta2/6), salmeterol produced a maximal cyclic AMP response that was only 22% that of that obtained with isoprenaline. In contrast in the higher expressing cells (CHO-beta2/ 4), the two maxima were of similar magnitude. 4. Salmeterol was a more potent stimulant of gene transcription, producing the same maximal response as isoprenaline in both cell lines. Furthermore, in the CHO-beta2/4 cells, Salmeterol was 50 fold more potent as a stimulant of SPAP secretion than of cyclic AMP accumulation. In contrast, isoprenaline was 24 fold less sensitive as a stimulant of SPAP secretion than of cyclic AMP accumulation. In the presence of serum (10%), the effects of both salmeterol and isoprenaline on gene transcription were augmented. 5. These data suggest that the low efficacy and/or long duration of action of salmeterol, favours a potent stimulation of gene transcription when compared to more efficacious but shorter-lived agonists such as isoprenaline.
Subject(s)
Adrenergic beta-Agonists/pharmacology , Albuterol/analogs & derivatives , Receptors, Adrenergic, beta-2/metabolism , Transcription, Genetic/drug effects , Albuterol/pharmacology , Alkaline Phosphatase/metabolism , Animals , CHO Cells , Cricetinae , Cricetulus , Cyclic AMP/metabolism , Dose-Response Relationship, Drug , Female , Humans , Iodocyanopindolol/metabolism , Isoproterenol/pharmacology , Receptors, Adrenergic, beta-2/genetics , Salmeterol Xinafoate , TransfectionABSTRACT
A transgenic animal can be defined as an organism that has undergone a stable modification of genotype as a result of genetic manipulation. Such animals are being increasingly employed as research and development tools by both academic and commercial institutions. The primary methods by which transgenic animals can be generated will be described. The relative merits of the approaches will be illustrated, as will their potential use in the discovery and development of novel therapeutic entities.
