Inhibition by phospholipid liposomes of the prolactin and cortisol response to insulin hypoglycemia in man

Abstract

This study was designed to further investigate the purported dopaminergic activity of phospholipid liposomes (PL) prepared from bovine cerebral extracts, and to obtain further indications about their pituitary or suprapituitary site of action. In eight normal subjects, we have studied the effects of PL administration (250 mg as IV bolus plus additional 250 mg infused IV over a 60-min period), compared to placebo, on the prolactin (PRL), cortisol and growth hormone (GH) response to an insulin tolerance test (ITT). In eight additional subjects, the effects of PL on the PRL and TSH response to TRH were evaluated. PL medication blunted the PRL and cortisol response in the ITT: significant differences, with respect to placebo administration, were observed between mean peak PRL values (51.9 +/- 13.63 SEM vs 83.4 +/- 26.35 ng/ml, P less than 0.05) and mean cortisol values at 120 min time (20.9 +/- 0.67 vs 26.7 +/- 2.46 micrograms/dl, P less than 0.05). In contrast, PL administration did not modify the ITT-related GH rise or the PRL and TSH release in response to TRH. These findings favour the view that PL are endowed with intrinsic biological activity which is dopamine-mediated, and point to the hypothalamus as their primary site of action.

Liposomes as potential masking agents in sport doping. Part 1: analysis of phospholipids and sphingomyelins in drugs and biological fluids by aqueous normal‐phase liquid chromatography‐tandem mass spectrometry

“…[15][16][17][18][19][20][21][22][23][24][25][26][27][28] Although PLs and SMs do not possess intrinsic and selective pharmacodynamic properties, they have also been extensively studied in pharmaceutical technology not only as excipients for pharmaceutical formulations, but also for the development of macromolecular constituents of carriers for drug delivery systems, and primarily among them liposomes. [29][30][31][32] In this context, the analysis of PLs and SMs is becoming of interest in sport doping analysis, too, since drug delivery systems, and especially those constituted by phospholipidic liposomes, have recently been suspected to be abused by the athletes to alter the pharmacokinetics of prohibited drugs [33,34] that, as such, are included in the Prohibited List of doping substances and methods of the World Anti-Doping Agency (WADA). [35] Particularly, the use of PS-based liposomial drugs, constituted only by the liposome carriers and without any active principle, commercially available in the European Union, has been repeatedly reported to be likely used 'off label' by ahtletes.…”