Effects of oral phosphocysteamine and rectal cysteamine in cystinosis

Determination of total cysteamine in human serum by a high-performance liquid chromatography with fluorescence detection

A convenient, reliable and rapid method for determination of total cysteamine in human plasma by high-performance liquid chromatography with fluorescence detection is reported. This assay involves reduction of samples with dithiothreitol, derivatization of total cysteamine by addition of monobromobimane and protein precipitation by perchloric acid. The calibration curve was linear in the range 2-150 nmol ml-1 and the detection limit was 0.5 nmol ml-1. This method was successfully applied for a pharmacokinetic study of three cysteamine derivatives in healthy volunteers without any interference from coexisting substances.

Inhibition of the proliferation of human neural neoplastic cell lines by cysteamine

Cysteamine (CySH), a thiol compound that crosses the blood-brain barrier, inhibited the proliferation of neural neoplastic cells in vitro. The IC50 of cysteamine with respect to inhibition after 72 h of drug exposure, was approximately 70 microM in the glioma cell line, 2607, and approximately 80 microM in the neuroblastoma cell line, DAOY. Interestingly, the inhibition of proliferation of 2607 cells produced by 72 h treatment with CySH could also be induced with exposure periods as short as 8 h. Another thiol bearing compound, penicillamine methyl ester, also arrested the proliferation of 2607 cells with IC50 approximately 160 microM. Cell cycle analysis revealed that CySH acted to lengthen the cell cycle period of 2607 cells by slowing the passage of cells through S phase and caused the cells to finally arrest in G2/M. In the other cell lines tested, CySH arrested cells in all phases of the cell cycle. These observations suggest that CySH and its congeners may have some utility in the treatment of neoplasia in vivo.

The treatment of cystinosis with cysteamine and phosphocysteamine in the United Kingdom and Eire

Fifty-nine patients with cystinosis were treated with cysteamine or phosphocysteamine in the United Kingdom up to May 1990. Treatment was started at a median age of 3.2 years (range 0.6-24.8 years) and continued for a median duration of 3.0 years (range 0.01-1.2 years). At the end of the study, 46 (78%) patients remained on treatment. One patient developed end-stage renal failure and 6 died. Efficacy was assessed in the 44 pre-transplant patients. The United Kingdom pre-transplant patients had significantly lower plasma creatinine concentrations at 6 and 8 years than a historical group of patients who did not receive cysteamine (P < 0.0001 and P < 0.0003, respectively). There was no significant difference between pretreatment and final post-treatment height standard deviation scores, suggesting maintenance of growth rate. The leucocyte cystine concentration was less than the accepted upper limit of the treatment range (1 nmol 1/2 cystine/mg protein) in only 21% of determinations. There was no significant difference between the mean pre-treatment and final values of leucocyte cystine concentration. The mean final doses of cysteamine (33 mg/kg per day) and phosphocysteamine (37 mg/kg per day base equivalent) were less than the mean dose (51 mg/kg per day) used in a United States multicentre trial. We conclude that cysteamine treatment was beneficial, but further improvements might be achieved by an improvement in monitoring of therapy.

Determination of total cysteamine in urine and plasma samples by gas chromatography with flame photometric detection

A sensitive and selective method for the determination of total cysteamine in urine and plasma samples by gas chromatography (GC) has been developed. After reduction of the sample with sodium borohydride, the liberated cysteamine was converted into its N,S-diisobutoxycarbonyl derivative and measured by GC with flame photometric detection using a DB-210 capillary column. The calibration curve was linear in the range 0.2-5.0 nmol, and the detection limit, at a signal-to-noise ratio of 3, was ca. 0.5 pmol injected. Using this method, total cysteamine in urine and plasma samples could be accurately and precisely determined without any interference from coexisting substances. Analytical results for the determination of total cysteamine in urine and plasma samples from normal subjects are presented.

Determination of sulphur amino acids by gas chromatography with flame photometric detection

A selective and sensitive method has been developed for the determination of sulphur amino acids by gas chromatography (GC). Sulphur amino acids were converted into their N(S)-isopropoxycarbonyl methyl ester derivatives and measured by GC with flame photometric detection using a DB-17 capillary column. The derivatives were sufficiently volatile and stable to give single symmetrical peaks. The detection limits of sulphur amino acids were ca. 0.5-1 pmol per injection, and the calibration curves were linear in the range 0.5-10 nmol for each sulphur amino acid. This method was successfully applied to small urine samples without prior clean-up, and sulphur amino acids in these samples could be analysed without any influence from coexisting substances. Overall recoveries of sulphur amino acids added to urine samples were 85-113%. The analytical results of free sulphur amino acid contents in urine samples of normal subjects are presented.

Determination of cysteamine and cystamine by gas chromatography with flame photometric detection

A gas chromatographic method for the determination of cysteamine and its disulphide cystamine is described. Cysteamine and cystamine are converted into N,S-diisobutoxycarbonyl and N,N-diisobutoxycarbonyl derivatives, respectively. The derivatives are analysed by gas chromatography with flame photometric detection, using a DB-210 capillary column. The calibration curves for cysteamine and cystamine in the range of 0.2-5.0 nmol are linear and sufficiently reproducible for quantitative analysis, and the detection limit is about 0.5 pmol injected. Cysteamine in mouse tissues is found in the free reduced, free oxidized and protein-bound forms. Free oxidized and protein-bound forms are reduced to free cysteamine by the use of sodium borohydride, and then derivatized. Cysteamine and cystamine in mouse tissues can be measured without any interference from coexisting substances by this method. The recoveries of cysteamine and cystamine added to the tissue samples are 91-106%, and their reproducibilities are found to be satisfactory. Analytical results for the determination of various forms of cysteamine in mouse tissues are presented.