Streptozocin diabetes alters immunoreactive beta-endorphin levels and pain perception after 8 wk in female rats.

Plasma, pituitary, and hypothalamic levels of the endogenous opioid peptide beta-endorphin were measured by radioimmunoassay and column chromatography in female rats 8 wk after the induction of diabetes with streptozocin (STZ) and in control female rats. In addition, pain perception was determined by measuring the latency to paw lick or jump after being placed on a hot plate. Plasma levels of immunoreactive beta-endorphin (IR-BE) were significantly reduced in STZ-induced diabetic female rats, as were the content and concentration of IR-BE in the neurointermediate lobe of the pituitary (NIL) and the content of IR-BE in the hypothalamus. The concentration but not the content of IR-BE in the anterior pituitary (AP) of the STZ-induced diabetic rats was increased significantly. Streptozocin-induced diabetes also resulted in a significant reduction in the total protein content of the AP, NIL, and hypothalamus. Column chromatography indicated that the decrease in IR-BE in the plasma, NIL, and hypothalamus represented a decrease in beta-endorphin, whereas the increase in IR-BE in the AP represented an increase in both beta-endorphin and beta-lipotropin. Diabetic animals consistently showed decreased latencies to paw lick or jump when subjected to hot-plate testing after 7 wk. These findings suggest that in female rats, central and peripheral endogenous opiate levels and tolerance to nociceptive thermal stimulation were diminished by 8 wk of chemically induced diabetes.

Diabetes induced by streptozocin results in a decrease in immunoreactive beta-endorphin levels in the pituitary and hypothalamus of female rats.

Immunoreactive beta-endorphin (IR-BE) was measured by radioimmunoassay in the anterior pituitary (AP), neurointermediate lobe of the pituitary (NIL), and hypothalamus of female rats 4 wk after being made diabetic by a single injection of streptozocin (STZ). STZ-induced diabetes resulted in a significant reduction in the content and concentration of IR-BE in the AP and the content of IR-BE in the hypothalamus. Total hypothalamic protein was also significantly diminished. IR-BE levels in the NIL were unchanged. Column chromatography indicated that the reduction in IR-BE in the AP of the diabetic female rats represented a decrease in peptides that co-eluted with beta-endorphin and beta-lipotropin. In the hypothalamus, the reduction in IR-BE was represented solely by a decrease in a peptide co-eluting with beta-endorphin. Beta-lipotropin was not detectable in the hypothalami of control or diabetic female rats. These results suggest that, in the rat, diabetes may produce alterations in the mechanism(s) that regulate endogenous opiate levels in the pituitary and hypothalamus.

Decreased pulsatile release of growth hormone in old male rats.

Pulsatile release of GH was compared in young (4-5 months old) and old (18-20 months old) male Sprague-Dawley rats using indwelling atrial cannulae. More than 57% of the young rats exhibited GH pulses greater than 300 ng/ml plasma, whereas only 7% of the old animals had GH pulses of similar amplitude. Trough GH values were not different between young and old rats, but during the 10.5-h sampling period, mean GH concentrations in young male rats were significantly greater than those in old male rats (175.3 +/- 20.9 vs. 70.2 +/- 7.6 ng/ml; P < 0.01). In another experiment, pituitary GH and hypothalamic somatostatin content were measured in young and old rats. The pituitary GH content was significantly greater in young than in old males (1187 +/- 95 vs. 670 +/- 93 microgram; P < 0.01). The immunoreactive somatostatin content in caudal areas of the hypothalamus was also greater in young than in old male rats (100.2 +/- 4.2 vs. 79.0 +/- 5.1 ng; P < 0.01). These observations demonstrate that GH secretion is depressed in old male rats, and this is associated with diminished pulsatile release of GH. The results also suggest that a relationship exists among the reduction in somatostatin content, pituitary GH content, and attenuated GH secretion in old male rats.

Decreased ability of old male rats to secrete luteinizing hormone (LH) is not due to alterations in pituitary LH-releasing hormone receptors.

The present study was undertaken to determine if the diminished release of LH in male rats with age in response to castration or LHRH injection is due to alternations in the number or affinity of LHRH receptors in the pituitary. Young (3-4 months old) and old (18-20 months) male Sprague-Dawley rats were killed 0, 2, 4, and 8 days after castration. Serum was collected for determination of LH concentrations, and anterior pituitaries were removed for analysis of LHRH receptors. The numbers and affinity constants of receptors were determined by Scatchard analysis using iodinated des-Gly10-[D-Ala6]LHRH ethylamide (LHRH-a) as ligand. Plasma LH in young rats increased from 54 ng/ml in intact animals to 319 ng/ml 8 days after castration, but in old animals, LH increased only from 47 to 119 ng/ml during the same period (P less than 0.01). However, there were no age-related differences in LHRH receptors in intact animals, and both young and old animals showed similar increases in pituitary LHRH receptors after castration when expressed either as receptors per pituitary (young, 132 +/- 27 to 262 +/- 43 fmol/pituitary; old, 175 +/- 27 to 299 +/- 19 fmol/pituitary) or as receptors per mg protein (young, 420 +/- 48 to 847 +/- 172 fmol/mg protein; old, 432 +/- 38 to 866 +/- 62 fmol/mg protein). Receptor affinity was not statistically different in intact young or old animals (4.51 +/- 0.41 X 10(9) and 4.51 +/- 1.23 X 10(9) M1, respectively), and receptor affinity increased in both groups in response to castration. The capacity of young and old male rats to produce LHRH receptors in response to exogenous LHRH was tested in a second experiment. Animals were castrated and given daily injections of testosterone propionate (500 micrograms/kg, im) for 13 days. Beginning on day 9, LHRH-a (250 micrograms/kg, sc) was injected for 5 days. The rises in serum LH after a single injection of LHRH-a were similar in young and old animals on the first and fifth days of LHRH-a treatment. LHRH receptors at the cessation of hormone therapy also increased similarly in both young and old animals in response to LHRH-a (715 +/- 135 and 811 +/- 203 fmol/mg protein, respectively). Receptor affinity was not statistically different in young (6.27 +/- 0.40 X 10(9) M-1) or old (6.67 +/- 0.79 X 10(9) M-1) animals. In a third experiment, male rats were castrated and given injections of LHRH (166 ng/kg) at 30-min intervals for 4.5 h.(ABSTRACT TRUNCATED AT 400 WORDS)

Release of immunoreactive beta-endorphin in vitro from pituitaries of young and old male rats.

The release of immunoreactive beta-endorphin (IR-BE) in vitro from the anterior pituitary (AP) and the neurointermediate lobe of the pituitary (NIL) from old male rats was significantly greater than from the AP and NIL from young male rats. In addition, the content and concentration of IR-BE in the AP and NIL was significantly greater in old than in young male rats, as was the concentration of IR-BE in the plasma. Chromatographic analysis revealed that in old male rats, the increase in IR-BE contained in and released by the AP and NIL, and found in the plasma, represented an increase in a peptide which coeluted with beta-endorphin rather than beta-lipotropin. These data suggest that both the AP and the NIL contribute to the elevation in plasma levels of IR-BE observed in old male rats, and that the increase in pituitary and plasma IR-BE in old male rats represents an increase in beta-endorphin.

The elevation of immunoreactive beta-endorphin in old male rats is related to alterations in dopamine and serotonin.

The concentration of immunoreactive beta-endorphin (IR-BE) in the anterior pituitary (AP) and the neurointermediate lobe of the pituitary (NIL) was elevated in old as compared to young male rats. Treatment of old male rats with the dopamine precursor, L-DOPA, did not affect the concentration of IR-BE in the AP and produced a significant reduction in the concentration of IR-BE in the NIL. By contrast, administration of the serotonergic neurotoxin, p-CPA, significantly diminished the concentration of IR-BE in the AP of old male rats, while the concentration of IR-BE in the NIL remained unchanged. Hypothalamic IR-BE was decreased in old male rats and was not influenced by administration of L-DOPA or p-CPA. Chromatographic analysis indicated that in the AP of old animals the amount of beta-endorphin relative to beta-lipotropin was increased and was diminished slightly by the treatments. Alterations in IR-BE in the NIL and hypothalamus were represented solely by beta-endorphin. These data suggest that in old male rats, a decrease in dopaminergic activity contributes to the increase in IR-BE levels in the NIL, and an increase in serotonergic function, at least in part, is responsible for the elevation in the level of IR-BE in the AP.

Immunoreactive beta-endorphin in the plasma, pituitary and hypothalamus of young and old male rats.

Immunoreactive beta-endorphin (IR-beta-ENDO) was measured in the plasma, pituitary, and hypothalamus of young (3-5 mo.) and old (19-23 mo.) male Sprague-Dawley rats, using a specific radioimmunoassay. Plasma IR-beta-ENDO in old male rats (3.44 +/- 0.54 ng/ml) was more than three times higher than values observed in young male rats (1.00 +/- 0.10 ng/ml). Pituitary content and concentration of IR-beta-ENDO also were significantly greater in the old (5.85 +/- 0.51 microgram/gland and 1.17 +/- 0.10 microgram/mg protein) than in the young (3.53 +/- 0.29 microgram/gland and 0.78 +/- 0.06 microgram/mg protein) male rats. The content of IR-beta-ENDO in the hypothalamus of old and young rats was nearly the same (43.45 +/- 2.47 and 49.88 +/- 6.35 ng/hypothalamus, respectively), whereas the concentration of IR-beta-ENDO in the hypothalamus of the old male rats (3.89 +/- 0.25 ng/mg protein) was approximately 50% lower than that observed in the young male rats (7,80 +/- 0.85 ng/mg protein). These changes in plasma, pituitary, and hypothalamic IR-beta-ENDO may contribute to the increase in prolactin and decrease in gonadotropins observed in old male rats, since beta-ENDO administration is known to produce these effects on prolactin and gonadotropin secretion.

Effect of thyrotropin-releasing hormone on microtubules in GH3 cells.

The effect of thyrotropin-releasing hormone (TRH) on the tubulin-microtubule system in GH3 cells was investigated. Prolactin (PRL) secretion by GH3 cells was stimulated by TRH at 1, 5, and 10 min of incubation. The polymerized tubulin levels increased from 0.4 units micrograms-1 protein in control cells to 0.6 units micrograms-1 protein in cells incubated with TRH for 1 min. Soluble tubulin levels increased from 0.8 units microgram-1 protein in control cells to 1.2 units micrograms-1 protein in cells exposed to TRH for 5 min. Tubulin levels were similar in control cells and cells treated with TRH for 10 min. These results suggest that TRH-stimulated PRL secretion is accompanied by a shift in the equilibrium between tubulin pools.

Neurotransmitters and estrogen interact to affect beta-endorphin levels in castrated female rats.

The possibility of an interaction between neurotransmitter systems and estrogen in affecting levels of immunoreactive beta-endorphin (IR-BE) in the anterior pituitary (AP), the neurointermediate lobe of the pituitary (NIL) and the hypothalamus was investigated in ovariectomized (OVX) female rats. Chronic administration of the dopamine antagonist, haloperidol (HALO), had no effect on IR-BE levels in the AP. By contrast, the content of IR-BE in the NIL was increased and the content of IR-BE in the hypothalamus was decreased by HALO. Chronic treatment with estradiol benzoate (EB) produced a decrease in IR-BE in all three tissues. The effect of EB on IR-BE levels in the AP and NIL was reversed by administration of HALO, while EB and HALO appeared to act independently on the hypothalamus. Gel chromatography indicated that alterations in IR-BE in the AP corresponded to similar changes in beta-endorphin (BE) and beta-lipotropin (LPH) and that BE alone comprised the immunoreactivity detected in the NIL and hypothalamus regardless of treatment. Chronic treatment with the alpha-adrenergic agonist, clonidine (CLON), increased, whereas treatment with EB decreased, IR-BE levels in the AP, NIL and hypothalamus. EB attenuated the effect of CLON on IR-BE levels in the AP and hypothalamus. Chronic treatment with CLON appeared to promote the formation of BE in the AP, whereas the proportions of BE and LPH were similar in the AP of controls and animals treated with EB or EB and CLON. BE alone was detected in the NIL and hypothalamus of treated and control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Mediation by gonadal steroids of plasma beta-endorphin and LH in castrated female and male rats.

Immunoreactive beta-endorphin (IR-BE) was significantly decreased and luteinizing hormone (LH) significantly increased in female rats castrated for four weeks. Forty eight hours after a single injection of estradiol benzoate (EB), IR-BE levels increased, and LH levels were reduced. On the afternoon following the administration of a second injection of EB given six hours earlier, IR-BE levels were reduced below control values, whereas LH levels were significantly elevated. There was no change in IR-BE levels during the remainder of that afternoon whereas LH levels decreased over time. Similar to female rats, IR-BE was diminished and LH increased in castrated male rats. IR-BE was increased significantly above those values observed in intact animals 24 hr after a single injection of TP and returned to control levels by 48 hr after administration of TP. Injection of TP reduced LH to levels observed prior to castration. These findings suggest that gonadal steroids exert a feedback on the release of IR-BE from the pituitary of female and male rats opposite to their feedback effect on the release of pituitary gonadotropins.

Characterization of beta-endorphin- and alpha-MSH-related peptides in rat heart.

POMC-derived peptides and mRNA have been identified in heart tissue, although POMC processing has not been fully characterized. In the present study, we found that beta-lipotropin and ACTH were localized in rat heart, although they were almost entirely converted to beta-endorphin- and alpha-MSH-related peptides. Ion exchange HPLC analysis revealed that beta-endorphin(1-31) was further processed to alpha-N-acetyl-beta-endorphin(1-31), which comprised 35.9 +/- 0.1% of total immunoreactivity, and smaller amounts of beta-endorphin(1-27), beta-endorphin(1-26), and their alpha-N-acetylated derivates. The predominant alpha-MSH immunoreactive peptides coeluted with alpha-MSH and N,O-diacetyl-alpha-MSH by reverse-phase HPLC, although small amounts of ACTH(1-13)-NH2 were also present. Thus, multiple forms of beta-endorphin and alpha-MSH are localized in rat heart. beta-Endorphin(1-31) is a minor constituent, however, indicating that nonopioid beta-endorphin peptides predominate.

The effects of immobilization stress on beta-endorphin levels are modulated by testosterone.

Immunoreactive beta-endorphin (IR-BE) levels were determined in the anterior pituitary (AP), neurointermediate lobe of the pituitary (NIL) and the hypothalamus of castrated male rats and castrated male rats treated with testosterone proprionate (TP), subsequent to exposure to acute (once for 45 min) or chronic (45 min each day for 15 consecutive days) immobilization stress. Acute stress resulted in a reduction in the concentration of IR-BE in the AP of castrated male rats, which was potentiated by TP. The concentration of IR-BE in the NIL was elevated by acute stress in castrated male rats and was not affected by acute stress in castrated male rats administered TP. Exposure to chronic immobilization stress elevated the concentration of IR-BE in the AP of castrated animals and not animals treated with TP. The concentration of IR-BE in the NIL of castrated animals was not altered by chronic immobilization. Chronic stress did result in a significant rise in the level of IR-BE in the NIL of castrated male rats given TP. Hypothlamic IR-BE levels in castrated male rats were reduced by TP and were not influenced by acute or chronic stress. Chromatographic analysis indicated that acute and chronic stress promoted the accumulation of beta-lipotropin rather than beta-endorphin in the AP. This effect was attenuated by TP. Beta-endorphin was the only form of immunoreactivity detected in the NIL and hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Demonstration by in situ hybridization of the proopiomelanocortin gene in the rat heart.

A biotinylated oligonucleotide probe was used to demonstrate the presence in the heart of the portion of the proopiomelanocortin messenger RNA which contains the sequence for beta-endorphin. The probe indicated the presence of beta-endorphin messenger RNA in cardiac tissue and specifically in the cardiac muscle cell. The probe also confirmed the well-documented presence of messenger RNA for beta-endorphin in the anterior and neurointermediate lobes of the pituitary. These findings indicate that in addition to the pituitary, beta-endorphin is produced in situ in the heart.

Beta-endorphin in the male rat pituitary: testosterone influences the effect of cocaine.

In order to determine if the effect of cocaine on the concentration of immunoreactive beta-endorphin (IR-BE) in the anterior pituitary (AP), neurointermediate lobe of the pituitary (NIL) and hypothalamus was modulated by gonadal steroid, the following groups of animals were studied: a) castrated male rats treated with vehicle, b) castrated male rats treated chronically with cocaine (daily for 10 days), c) castrated male rats treated with testosterone propionate (TP) and d) castrated male rats treated with TP and chronically administered cocaine. Only in castrated rats given TP did cocaine induce a significant increase in the concentration of IR-BE in the AP. The concentration of IR-BE in the NIL was increased by cocaine and was not influenced by the presence or absence of TP. Hypothalamic IR-BE remained unchanged in response to cocaine and was decreased by TP. Column chromatography revealed that TP and cocaine interacted to modulate the amount of beta-endorphin relative to beta-lipotropin in the AP. These findings suggest that in the male rat, the effect of cocaine on the concentration of IR-BE in the AP is modulated by the gonadal steroid environment. By contrast, gonadal does not appear to play a role in the effect of cocaine on the concentration of IR-BE in the NIL.

Cocaine and inhibition of nitric oxide synthesis produce opioid-mediated antinociception.

Cocaine and nitric oxide are known to influence the perception of pain. The present study sought to determine if the endogenous opioid peptide system participates in cocaine-induced antinociception and antinociception produced by antagonism of nitric oxide. Pain perception was measured using the hot plate test. Administration of cocaine (25 mg/kg) to male rats resulted in a significant increase in reaction time in the hot plate test, which was reversed by treatment with 3, 10, and 30 mg/kg of the opiate antagonist, naloxone. In rats that were not treated with cocaine, doses of 30 and 60 mg/kg of naloxone significantly reduced hot plate reaction Time. Treatment of animals with the nitric oxide synthase inhibitor, N omega nitro-L-arginine, produced a significant increase in response time to the hot plate, which was reversed by administration of naloxone. These data indicate that antinociception produced in the rat by cocaine appears to have a supraspinal component and to involve activation of endogenous opioid peptide activity in the brain. The results also suggest a tonic inhibition of endogenous opioid peptide activity by nitric oxide, which when antagonized, results in diminished response to pain.

Sign of lipid peroxidation as measured in the urine of patients with probable Alzheimer's disease.

Free radical-induced oxidative damage may be involved in the neurodegenerative process associated with Alzheimer's disease (AD). 8-Isoprostaglandin F(2alpha) (iPF(2alpha)-III) is an isoprostane derived from free radical-induced non-enzymatic oxidation of arachidonic acid. It is formed in vivo and is an indicator of lipid peroxidation. Measurements were made of iPF(2alpha)-III in the urine of patients with mild to moderate dementia associated with probable AD and compared to those in the urine of non-demented subjects, who were similar in age and gender. 2,3-Dinor thromboxane B(2) (dinor TXB(2)), a urinary metabolite of TXB(2) was also measured, and served as an indicator of the enzymatic transformation of a product of arachidonic acid. Enzyme linked immunoassays were used to measure iPF(2alpha)-III and dinor TXB(2) in the urine. The concentration of iPF(2alpha)-III was significantly elevated in urine of patients assessed to have mild to moderate dementia as compared to non-demented patients. The concentration of urinary dinor TXB(2) was also significantly elevated in the patients with dementia and probable AD as compared to the non-demented subjects. There was considerable overlap of values obtained for demented and non-demented patients for iPF(2alpha)-III and dinor TXB(2), respectively. The observed elevation of iPF(2alpha)-III suggests that patients with mild to moderate dementia associated with probable AD are experiencing significant oxidative stress. This finding is consistent with current data suggesting that oxidative stress may be occurring in patients with dementia and probable AD. The increase of dinor TXB(2) may indicate that enzymatic processes related to the metabolism of arachidonic acid-derived products are also increased in demented patients with probable AD.

NMDA receptor antagonism produces antinociception which is partially mediated by brain opioids and dopamine.

Inhibition of nitric oxide synthase (NOS) activity results in opioid-mediated supraspinal analgesia in the rat, as indicated by increased reaction time in the hot plate test. It is documented that a relationship exists between NMDA receptor activation and the activity of NOS. The present investigation sought to determine if inactivation of the NMDA receptor produced antinociception of supraspinal origin, as was observed in response to inhibition of NOS, and if this response was mediated by brain opioids, by activation of receptors for the neurotransmitter, dopamine, or both. Administration of MK-801, a non-competitive antagonist of the NMDA receptor, produced significant antinociception as measured by reaction time in the hot plate test of analgesia. Antinociception resulting from treatment with MK-801 appeared to be mediated by brain opioids, as indicated by the ability of the opioid antagonist, naloxone, to partially reverse the effect of MK-801 administration. This analgesic response was also partially diminished by administration of the dopamine D1 receptor antagonist, SCH 23390 and the dopamine D2 receptor antagonist, sulpiride. The analgesia resulting from NMDA receptor antagonism was found to be only partially attributable to dopamine and brain opioids, since co-administration of naloxone and SCH 23390 or naloxone and sulpiride, were unable to completely reverse the antinociceptive response to MK-801. The present findings suggest that inhibition of NMDA receptor activity produces supraspinal analgesia. Furthermore, it appears that antinociception induced by blockade of the NMDA receptor results, at least in part, from activation of endogenous brain opioids and stimulation of D1 and D2 subtypes of the dopamine receptor.

Cocaine influences beta-endorphin levels and release.

Immunoreactive beta-endorphin (IR-BE) was measured in the plasma, anterior pituitary (AP), neurointermediate lobe of the pituitary (NIL) and hypothalamus of male rats treated chronically (once daily for ten days) with cocaine. Cocaine produced a consistent elevation in the concentration of IR-BE in the plasma, the AP and the NIL at doses of 2.5 - 20 mg/kg/ip. The release of IR-BE from the AP and the NIL was determined in vitro and was found to be increased by treatment with cocaine. Chronic administration of cocaine did not affect the concentration of IR-BE in the hypothalamus. Chromatographic analysis revealed that cocaine produced a slight decrease in the amount of beta-endorphin relative to beta-lipotropin in the AP. Beta-endorphin was the major form of IR-BE released by the AP and the sole constituent and secretory product of the NIL. These data indicate that chronic administration of cocaine stimulates the endogenous opiate system, elevating the levels of IR-BE in the pituitary and promoting beta-endorphin release.

Administration of gonadal steroids to neonatal rats affects beta-endorphin levels in the adult.

Administration of gonadal steroids to neonatal rats has a profound effect on the function of the neuroendocrine system in the adult animal. Considering that gonadal steroids modulate hypothalamic and pituitary levels of beta-endorphin (BE) in adult male and female rats, the effects of neonatal gonadal steroid treatment on BE levels in the adult animal were investigated. Neonatal male rats were administered testosterone and neonatal female rats were treated with estrogen. Matched control littermates received vehicle. All animals were sacrificed at 90 days of age. Neonatal gonadal steroid treatment did not affect the level of immunoreactive beta-endorphin (IR-BE) in the anterior pituitary (AP) of male rats but did result in a significant increase in IR-BE in the AP of female rats. Neonatal administration of gonadal steroids produced a significant decrease in IR-BE in the neurointermediate lobe of the pituitary (NIL) of both male and female rats, with the magnitude of the decrease being greater in the NIL of the female rats. IR-BE levels in the hypothalamus of male or female rats were not altered by the treatments. Column chromatography indicated that the increase in IR-BE in the AP represented a proportional increase in BE and beta-lipotropin, while the reduction in IR-BE in the NIL of the treated rats represented a reduction in BE. These findings suggest that gonadal steroids may influence the development of the neurotransmitter systems which regulate BE levels in the adult pituitary, the development of the biosynthetic mechanisms of the adult pituitary, or both.

Enzyme immunoassays (EIAs) of eicosanoids.

Enzyme immunoassay of eicosanoids is a nonradioactive, highly sensitive method of determining the concentration of eicosanoids in biological samples. Although relatively easy to use, the assays require a high level of precise pipetting technique and familiarity with critical points in the assay procedure. Although assay kits complete with plates, buffers, antibodies, tracers, and color development reagents are available, it is more economical to develop the assay within the laboratory if the assay is to be performed routinely. The only major disadvantage with EIA is that the investigator is limited to measuring eicosanoids with commercially available enzyme-tracers and antibodies. The labeling of particular eicosanoids by enzyme tracers is rarely, if ever, performed outside of industry. Growing of antibodies is conducted in many laboratories but is beyond the scope of this chapter. It requires a significant level of commitment of time and resources to establish the specificity of the antibody (i.e., does the antibody cross-react with eicosanoids of similar structure). Furthermore, this will not solve the problem of availability of eicosanoid-tracer. On the other hand, it must be noted that with the exception of the cytochrome P-450 metabolites of arachidonic acid, most of the major eicosanoids that are biologically active and are known to play regulatory roles in physiology and/or pathology, have commercially available antibodies and enzyme-tracers.